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• Squid proxy not serving modified html content

  - by Matthew

  I'm trying to use squid to modify the page content of web page requests. I followed the upside-down-ternet tutorial which showed instructions for how to flip images on pages. I need to change the actual html of the page. I've been trying to do the same thing as in the tutorial, but instead of editing the image I'm trying to edit the html page. Below is a php script I'm using to try to do it. All jpg images get flipped, but the content on the page does not get edited. The edited index.html files written contain the edited content, but the pages the users receive don't contain the edited content. #!/usr/bin/php <?php $temp = array(); while ( $input = fgets(STDIN) ) { $micro_time = microtime(); // Split the output (space delimited) from squid into an array. $temp = split(' ', $input); //Flip jpg images, this works correctly if (preg_match("/.*\.jpg/i", $temp[0])) { system("/usr/bin/wget -q -O /var/www/cache/$micro_time.jpg ". $temp[0]); system("/usr/bin/mogrify -flip /var/www/cache/$micro_time.jpg"); echo "http://127.0.0.1/cache/$micro_time.jpg\n"; } //Don't edit files that are obviously not html. $temp[0] contains url of file to get elseif (preg_match("/(jpg|png|gif|css|js|\(|\))/i", $temp[0], $matches)) { echo $input; } //Otherwise, could be html (e.g. `wget http://www.google.com` downloads index.html) else{ $time = time() . microtime(); //For unique directory names $time = preg_replace("/ /", "", $time); //Simplify things by removing the spaces mkdir("/var/www/cache/". $time); //Create unique folder system("/usr/bin/wget -q --directory-prefix=\"/var/www/cache/$time/\" ". $temp[0]); $filename = system("ls /var/www/cache/$time/"); //Get filename of downloaded file //File is html, edit the content (this does not work) if(preg_match("/.*\.html/", $filename)){ //Get the html file contents $contentfh = fopen("/var/www/cache/$time/". $filename, 'r'); $content = fread($contentfh, filesize("/var/www/cache/$time/". $filename)); fclose($contentfh); //Edit the html file contents $content = preg_replace("/<\/body>/i", "<!-- content served by proxy --></body>", $content); //Write the edited file $contentfh = fopen("/var/www/cache/$time/". $filename, 'w'); fwrite($contentfh, $content); fclose($contentfh); //Return the edited page echo "http://127.0.0.1/cache/$time/$filename\n"; } //Otherwise file is not html, don't edit else{ echo $input; } } } ?>

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• Creating a System::String object from a BSTR in Managed C++ - is this way a good idea???

  - by Eli

  My co-worker is filling a System::String object with double-byte characters from an unmanaged library by the following method: RFC_PARAMETER aux; Object* target; RFC_UNICODE_TYPE_ELEMENT* elm; elm = &(m_coreObject->m_pStructMeta->m_typeElements[index]); aux.name = NULL; aux.nlen = 0; aux.type = elm->type; aux.leng = elm->c2_length; aux.addr = m_coreObject->m_rfcWa + elm->c2_offset; GlobalFunctions::CreateObjectForRFCField(target,aux,elm->decimals); GlobalFunctions::ReadRFCField(target,aux,elm->decimals); Where GlobalFunctions::CreateObjectForRFCField creates a System::String object filled with spaces (for padding) to what the unmanaged library states the max length should be: static void CreateObjectForRFCField(Object*& object, RFC_PARAMETER& par, unsigned dec) { switch (par.type) { case TYPC: object = new String(' ',par.leng / sizeof(_TCHAR)); break; // unimportant afterwards. } } And GlobalFunctions::ReadRFCField() copies the data from the library into the created String object and preserves the space padding: static void ReadRFCField(String* target, RFC_PARAMETER& par) { int lngt; _TCHAR* srce; switch (par.type) { case TYPC: case TYPDATE: case TYPTIME: case TYPNUM: lngt = par.leng / sizeof(_TCHAR); srce = (_TCHAR*)par.addr; break; case RFCTYPE_STRING: lngt = (*(_TCHAR**)par.addr != NULL) ? (int)_tcslen(*(_TCHAR**)par.addr) : 0; srce = *(_TCHAR**)par.addr; break; default: throw new DotNet_Incomp_RFCType2; } if (lngt > target->Length) lngt = target->Length; GCHandle gh = GCHandle::Alloc(target,GCHandleType::Pinned); wchar_t* buff = reinterpret_cast<wchar_t*>(gh.AddrOfPinnedObject().ToPointer()); _wcsnset(buff,' ',target->Length); _snwprintf(buff,lngt,_T2WFSP,srce); gh.Free(); } Now, on occasion, we see access violations getting thrown in the _snwprintf call. My question really is: Is it appropriate to create a string padded to a length (ideally to pre-allocate the internal buffer), and then to modify the String using GCHandle::Alloc and the mess above. And yes, I know that System::String objects are supposed to be immutable - I'm looking for a definitive "This is WRONG and here is why". Thanks, Eli.

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• Queue ExternalInterface calls to Flash Object in UpdatePanel - Needs Improvement?

  - by Laramie

  A Flash (actually Flex) object is created on an ASP.Net page within an Update Panel using a modified version of the embedCallAC_FL_RunContent.js script so it can be written in dynamically. It is re-created with this script with each partial postback to that panel. There are also other Update Panels on the page. With some postbacks (partial and full), External Interface calls such as $get('FlashObj').ExternalInterfaceFunc('arg1', 0, true); are prepared server-side and added to the page using ScriptManager.RegisterStartupScript. They're embedded in a function and stuffed into Sys.Application's load event, for example Sys.Application.add_load(funcContainingExternalInterfaceCalls). The problem is that because the Flash object's state state may change with each partial postback, the Flash (Flex) object and/or External Interface may not be ready or even exist yet in the DOM when the JavaScript - Flash External Interface call is made. It results in an "Object doesn't support this property or method" exception. I have a working strategy to make the ExternalInterface calls immediately if Flash is ready or else queue them until such time that Flash announces its readiness. //Called when the Flash object is initialized and can accept ExternalInterfaceCalls var flashReady = false; //Called by Flash when object is fully initialized function setFlashReady() { flashReady = true; //Make any queued ExternalInterface calls, then dequeue while (extIntQueue.length > 0) (extIntQueue.shift())(); } var extIntQueue = []; function callExternalInterface(flashObjName, funcName, args) { //reference to the wrapped ExternalInterface Call var wrapped = extWrap(flashObjName, funcName, args); //only procede with ExternalInterface call if the global flashReady variable has been set if (flashReady) { wrapped(); } else { //queue the function so when flashReady() is called next, the function is called and the aruments are passed. extIntQueue.push(wrapped); } } //bundle ExtInt call and hold variables in a closure function extWrap(flashObjName, funcName, args) { //put vars in closure return function() { var funcCall = '$get("' + flashObjName + '").' + funcName; eval(funcCall).apply(this, args); } } I set the flashReady var to dirty whenever I update the Update Panel that contains the Flash (Flex) object. ScriptManager.RegisterClientScriptBlock(parentContainer, parentContainer.GetType(), "flashReady", "flashReady = false;", true); I'm pleased that I got it to work, but it feels like a hack. I am still on the learning curve with respect to concepts like closures why "eval()" is apparently evil, so I'm wondering if I'm violating some best practice or if this code should be improved, if so how? Thanks.

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• How to create multiple Repository object inside a Repository class using Unit Of Work?

  - by Santosh

  I am newbie to MVC3 application development, currently, we need following Application technologies as requirement MVC3 framework IOC framework – Autofac to manage object creation dynamically Moq – Unit testing Entity Framework Repository and Unit Of Work Pattern of Model class I have gone through many article to explore an basic idea about the above points but still I am little bit confused on the “Repository and Unit Of Work Pattern “. Basically what I understand Unit Of Work is a pattern which will be followed along with Repository Pattern in order to share the single DB Context among all Repository object, So here is my design : IUnitOfWork.cs public interface IUnitOfWork : IDisposable { IPermitRepository Permit_Repository{ get; } IRebateRepository Rebate_Repository { get; } IBuildingTypeRepository BuildingType_Repository { get; } IEEProjectRepository EEProject_Repository { get; } IRebateLookupRepository RebateLookup_Repository { get; } IEEProjectTypeRepository EEProjectType_Repository { get; } void Save(); } UnitOfWork.cs public class UnitOfWork : IUnitOfWork { #region Private Members private readonly CEEPMSEntities context = new CEEPMSEntities(); private IPermitRepository permit_Repository; private IRebateRepository rebate_Repository; private IBuildingTypeRepository buildingType_Repository; private IEEProjectRepository eeProject_Repository; private IRebateLookupRepository rebateLookup_Repository; private IEEProjectTypeRepository eeProjectType_Repository; #endregion #region IUnitOfWork Implemenation public IPermitRepository Permit_Repository { get { if (this.permit_Repository == null) { this.permit_Repository = new PermitRepository(context); } return permit_Repository; } } public IRebateRepository Rebate_Repository { get { if (this.rebate_Repository == null) { this.rebate_Repository = new RebateRepository(context); } return rebate_Repository; } } } PermitRepository .cs public class PermitRepository : IPermitRepository { #region Private Members private CEEPMSEntities objectContext = null; private IObjectSet<Permit> objectSet = null; #endregion #region Constructors public PermitRepository() { } public PermitRepository(CEEPMSEntities _objectContext) { this.objectContext = _objectContext; this.objectSet = objectContext.CreateObjectSet<Permit>(); } #endregion public IEnumerable<RebateViewModel> GetRebatesByPermitId(int _permitId) { // need to implment } } PermitController .cs public class PermitController : Controller { #region Private Members IUnitOfWork CEEPMSContext = null; #endregion #region Constructors public PermitController(IUnitOfWork _CEEPMSContext) { if (_CEEPMSContext == null) { throw new ArgumentNullException("Object can not be null"); } CEEPMSContext = _CEEPMSContext; } #endregion } So here I am wondering how to generate a new Repository for example “TestRepository.cs” using same pattern where I can create more then one Repository object like RebateRepository rebateRepo = new RebateRepository () AddressRepository addressRepo = new AddressRepository() because , what ever Repository object I want to create I need an object of UnitOfWork first as implmented in the PermitController class. So if I would follow the same in each individual Repository class that would again break the priciple of Unit Of Work and create multiple instance of object context. So any idea or suggestion will be highly appreciated. Thank you

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• Move an object in the direction of a bezier curve?

  - by Sent1nel

  I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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• How does interpolation actually work to smooth out an object's movement?

  - by user22241

  I've asked a few similar questions over the past 8 months or so with no real joy, so I am going make the question more general. I have an Android game which is OpenGL ES 2.0. within it I have the following Game Loop: My loop works on a fixed time step principle (dt = 1 / ticksPerSecond) loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ updateLogic(dt); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; } render(); My intergration works like this: sprite.posX+=sprite.xVel*dt; sprite.posXDrawAt=sprite.posX*width; Now, everything works pretty much as I would like. I can specify that I would like an object to move across a certain distance (screen width say) in 2.5 seconds and it will do just that. Also because of the frame skipping that I allow in my game loop, I can do this on pretty much any device and it will always take 2.5 seconds. Problem However, the problem is that when a render frame skips, the graphic stutter. It's extremely annoying. If I remove the ability to skip frames, then everything is smooth as you like, but will run at different speeds on different devices. So it's not an option. I'm still not sure why the frame skips, but I would like to point out that this is Nothing to do with poor performance, I've taken the code right back to 1 tiny sprite and no logic (apart from the logic required to move the sprite) and I still get skipped frames. And this is on a Google Nexus 10 tablet (and as mentioned above, I need frame skipping to keep the speed consistent across devices anyway). So, the only other option I have is to use interpolation (or extrapolation), I've read every article there is out there but none have really helped me to understand how it works and all of my attempted implementations have failed. Using one method I was able to get things moving smoothly but it was unworkable because it messed up my collision. I can foresee the same issue with any similar method because the interpolation is passed to (and acted upon within) the rendering method - at render time. So if Collision corrects position (character now standing right next to wall), then the renderer can alter it's position and draw it in the wall. So I'm really confused. People have said that you should never alter an object's position from within the rendering method, but all of the examples online show this. So I'm asking for a push in the right direction, please do not link to the popular game loop articles (deWitters, Fix your timestep, etc) as I've read these multiple times. I'm not asking anyone to write my code for me. Just explain please in simple terms how Interpolation actually works with some examples. I will then go and try to integrate any ideas into my code and will ask more specific questions if need-be further down the line. (I'm sure this is a problem many people struggle with).

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• systemstate dump ??

  - by JaneZhang(???)

          ???????????????hang????,????????systemstate dump?????????,?????,????????,???????????????,????systemstate dump?????????????       ??????,????????systemstate dump, ?????“WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK”?        systemstate dump???????????,??????:??????,???????,????dump????????,???????M????)1. ?sysdba???????:$sqlplus / as sysdba??$sqlplus -prelim / as sysdba <==??????????hang?????SQL>oradebug setmypidSQL>oradebug unlimit;SQL>oradebug dump systemstate 266;?1~2??SQL>oradebug dump systemstate 266;?1~2??SQL>oradebug dump systemstate 266;SQL>oradebug tracefile_name;==>????????2. ????systemstate dump,??????hang analyze??????????????????$sqlplus / as sysdba??$sqlplus -prelim / as sysdba <==??????????hang?????SQL>oradebug setmypidSQL>oradebug unlimit;SQL>oradebug dump hanganalyze 3?1~2??SQL>oradebug dump hanganalyze 3?1~2??SQL>oradebug dump hanganalyze 3SQL>oradebug tracefile_name;==>??????????RAC???,????????????systemstate dump,???????????(?????????):$sqlplus / as sysdba??$sqlplus -prelim / as sysdba <==??????????hang?????SQL>oradebug setmypidSQL>oradebug unlimitSQL>oradebug -g all dump systemstate 266  <==-g all ??????????dump?1~2??SQL>oradebug -g all dump systemstate 266?1~2??SQL>oradebug -g all dump systemstate 266?RAC???hang analyze:SQL>oradebug setmypidSQL>oradebug unlimitSQL>oradebug -g all hanganalyze 3?1~2??SQL>oradebug -g all hanganalyze 3?1~2??SQL>oradebug -g all hanganalyze 3?????????????????systemstate dump,?????????????backgroud_dump_dest??diag trace???????????????????????????,?????hang?,?????systemstate dump?????:10:   dump11:   dump + global cache of RAC256: short stack (????)258: dump(???lock element) + short stack (????)266: 256+10 -->short stack+ dump267: 256+11 -->short stack+ dump + global cache of RAClevel 11? 267? dump global cache, ??????trace ??,??????????????,????????,???266,??????dump?????????,????????????????????short stack????,???????,??2000???,??????30??????????,????level 10 ?? level 258, level 258 ? level 10????short short stack, ??level 10?????lock element data.?????systemstate dump???,??????level?????:??????37???:-rw-r----- 1 oracle oinstall    72721 Aug 31 21:50 rac10g2_ora_31092.trc==>256 (short stack, ????2K)-rw-r----- 1 oracle oinstall  2724863 Aug 31 21:52 rac10g2_ora_31654.trc==>10    (dump,????72K )-rw-r----- 1 oracle oinstall  2731935 Aug 31 21:53 rac10g2_ora_32214.trc==>266 (dump + short stack ,????72K)RAC:-rw-r----- 1 oracle oinstall 55873057 Aug 31 21:49 rac10g2_ora_30658.trc ==>11   (dump+global cache,????1.4M)-rw-r----- 1 oracle oinstall 55879249 Aug 31 21:48 rac10g2_ora_28615.trc ==>267 (dump+global cache+short stack,????1.4M) ??,??????dump global cache(level 11?267,???????????????)??????????,?????????systemstate dump ??

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• StackOverflowException throws often when .net application built with Debug mode

  - by user1487950

  I have an application which access an external webservice often, when i are trying to debug it, means debuging in vistual studio. it often throws out StackOverflowException at the webserverice call point. when building in Release mode , the exception thrown out only occasionally. I checked the call stack, looks like there is no recursive call. can you please suggest? thank you very much. call statck attached. [In a sleep, wait, or join] mscorlib.dll!System.Threading.WaitHandle.InternalWaitOne(System.Runtime.InteropServices.SafeHandle waitableSafeHandle, long millisecondsTimeout, bool hasThreadAffinity, bool exitContext) + 0x2b bytes mscorlib.dll!System.Threading.WaitHandle.WaitOne(int millisecondsTimeout, bool exitContext) + 0x2d bytes System.dll!System.Net.NetworkAddressChangePolled.CheckAndReset() + 0x9d bytes System.dll!System.Net.NclUtilities.LocalAddresses.get() + 0x49 bytes System.dll!System.Net.WebProxyScriptHelper.myIpAddress() + 0x27 bytes [Native to Managed Transition] System.dll!System.Net.WebProxyScriptHelper.MyMethodInfo.Invoke(object target, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, object[] args, System.Globalization.CultureInfo culture) + 0x6b bytes MTOqoHCT.dll!JScript 0.myIpAddress(object this, Microsoft.JScript.Vsa.VsaEngine vsa Engine, object arguments) + 0x91 bytes MTOqoHCT.dll!JScript 0.FindProxyForURL(object this, Microsoft.JScript.Vsa.VsaEngine vsa Engine, object arguments, object url, object host) + 0x3c6e bytes MTOqoHCT.dll!__WebProxyScript.__WebProxyScript.ExecuteFindProxyForURL(object url, object host) + 0x11d bytes [Native to Managed Transition] Microsoft.JScript.dll!System.Net.VsaWebProxyScript.CallMethod(object targetObject, string name, object[] args) + 0x11a bytes Microsoft.JScript.dll!System.Net.VsaWebProxyScript.Run(string url, string host) + 0x74 bytes [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage msg, int methodPtr, bool fExecuteInContext) + 0x1ef bytes mscorlib.dll!System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage msg) + 0xf bytes mscorlib.dll!System.Runtime.Remoting.Messaging.ServerObjectTerminatorSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x66 bytes mscorlib.dll!System.Runtime.Remoting.Messaging.ServerContextTerminatorSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x8a bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossContextChannel.SyncProcessMessageCallback(object[] args) + 0x94 bytes mscorlib.dll!System.Threading.Thread.CompleteCrossContextCallback(System.Threading.InternalCrossContextDelegate ftnToCall, object[] args) + 0x8 bytes [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.Runtime.Remoting.Channels.CrossContextChannel.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0xa7 bytes mscorlib.dll!System.Runtime.Remoting.Channels.ChannelServices.SyncDispatchMessage(System.Runtime.Remoting.Messaging.IMessage msg) + 0x92 bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoDispatch(byte[] reqStmBuff, System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage smuggledMcm, out System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage smuggledMrm) + 0xed bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatchCallback(object[] args) + 0x8a bytes mscorlib.dll!System.Threading.Thread.CompleteCrossContextCallback(System.Threading.InternalCrossContextDelegate ftnToCall, object[] args) + 0x8 bytes [Appdomain Transition] mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatch(byte[] reqStmBuff, System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage smuggledMcm, out System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage smuggledMrm) + 0x74 bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0xa3 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.CallProcessMessage(System.Runtime.Remoting.Messaging.IMessageSink ms, System.Runtime.Remoting.Messaging.IMessage reqMsg, System.Runtime.Remoting.Contexts.ArrayWithSize proxySinks, System.Threading.Thread currentThread, System.Runtime.Remoting.Contexts.Context currentContext, bool bSkippingContextChain) + 0x50 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.InternalInvoke(System.Runtime.Remoting.Messaging.IMethodCallMessage reqMcmMsg, bool useDispatchMessage, int callType) + 0x1d5 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x66 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(ref System.Runtime.Remoting.Proxies.MessageData msgData, int type) + 0xee bytes System.dll!System.Net.NetWebProxyFinder.GetProxies(System.Uri destination, out System.Collections.Generic.IList<string> proxyList) + 0x83 bytes System.dll!System.Net.AutoWebProxyScriptEngine.GetProxies(System.Uri destination, out System.Collections.Generic.IList<string> proxyList, ref int syncStatus) + 0x84 bytes System.dll!System.Net.WebProxy.GetProxiesAuto(System.Uri destination, ref int syncStatus) + 0x2e bytes System.dll!System.Net.ProxyScriptChain.GetNextProxy(out System.Uri proxy) + 0x2e bytes System.dll!System.Net.ProxyChain.ProxyEnumerator.MoveNext() + 0x98 bytes System.dll!System.Net.ServicePointManager.FindServicePoint(System.Uri address, System.Net.IWebProxy proxy, out System.Net.ProxyChain chain, ref System.Net.HttpAbortDelegate abortDelegate, ref int abortState) + 0x120 bytes System.dll!System.Net.HttpWebRequest.FindServicePoint(bool forceFind) + 0xb1 bytes System.dll!System.Net.HttpWebRequest.GetRequestStream(out System.Net.TransportContext context) + 0x247 bytes System.dll!System.Net.HttpWebRequest.GetRequestStream() + 0xe bytes System.Web.Services.dll!System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(string methodName, object[] parameters) + 0xc0 bytes Gfinet.Config.dll!Gfinet.Config.Service.cfg_webservice.addOrUpdateProperties(string string, int intVal, Gfinet.Config.Service.PropertiesDataM[] propertiesDataMs) + 0xa3 bytes Gfinet.Config.dll!Gfinet.Config.Service.WSServiceImpl.AddOrUpdateProperties(int setId, Gfinet.Config.Service.PropertiesDataM[] properties) + 0x46 bytes [Native to Managed Transition] Gfinet.Config.dll!Gfinet.Config.Service.ServiceAspect.InvocationHandler(object target, System.Reflection.MethodBase method, object[] parameters) + 0x49e bytes Gfinet.Config.dll!Gfinet.Config.DynamicProxy.DynamicProxyImpl.Invoke(System.Runtime.Remoting.Messaging.IMessage message) + 0x110 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(ref System.Runtime.Remoting.Proxies.MessageData msgData, int type) + 0xee bytes Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.StoreElement(string application, string category, string id, string elementValue, bool save) Line 303 + 0x55 bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAllInternal() Line 582 + 0x6e bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAll(bool async) Line 434 + 0x8 bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAll() Line 406 + 0xa bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Container.Persistor.Save() Line 59 + 0xc bytes C# Spark.exe!Tici.Kraps.RibbonShell.OnBtnSaveWorkspaceItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e) Line 642 + 0xf bytes C# DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItem.OnClick(DevExpress.XtraBars.BarItemLink link) + 0x108 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarBaseButtonItem.OnClick(DevExpress.XtraBars.BarItemLink link) + 0x47 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkClick() + 0x245 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkAction(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0xb3 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarButtonItemLink.OnLinkAction(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0x47e bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkActionCore(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0x82 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.ViewInfo.BarSelectionInfo.ClickLink(DevExpress.XtraBars.BarItemLink link) + 0x85 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.ViewInfo.BarSelectionInfo.UnPressLink(DevExpress.XtraBars.BarItemLink link) + 0x1e5 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnUnPressItem(DevExpress.Utils.DXMouseEventArgs e, DevExpress.XtraBars.Ribbon.ViewInfo.RibbonHitInfo hitInfo) + 0xa7 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnUnPress(DevExpress.Utils.DXMouseEventArgs e, DevExpress.XtraBars.Ribbon.ViewInfo.RibbonHitInfo hitInfo) + 0x5f bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnMouseUp(DevExpress.Utils.DXMouseEventArgs e) + 0x19a bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.RibbonHandler.OnMouseUp(DevExpress.Utils.DXMouseEventArgs e) + 0x47 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.RibbonControl.OnMouseUp(System.Windows.Forms.MouseEventArgs e) + 0x95 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.WmMouseUp(ref System.Windows.Forms.Message m, System.Windows.Forms.MouseButtons button, int clicks) + 0x2d1 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.WndProc(ref System.Windows.Forms.Message m) + 0x93a bytes DevExpress.Utils.v11.2.dll!DevExpress.Utils.Controls.ControlBase.WndProc(ref System.Windows.Forms.Message m) + 0x81 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.RibbonControl.WndProc(ref System.Windows.Forms.Message m) + 0x85 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.OnMessage(ref System.Windows.Forms.Message m) + 0x13 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.WndProc(ref System.Windows.Forms.Message m) + 0x31 bytes System.Windows.Forms.dll!System.Windows.Forms.NativeWindow.Callback(System.IntPtr hWnd, int msg, System.IntPtr wparam, System.IntPtr lparam) + 0x96 bytes [Native to Managed Transition] [Managed to Native Transition] DevExpress.Utils.v11.2.dll!DevExpress.Utils.Win.Hook.ControlWndHook.WindowProc(System.IntPtr hWnd, int message, System.IntPtr wParam, System.IntPtr lParam) + 0x159 bytes [Native to Managed Transition] [Managed to Native Transition] System.Windows.Forms.dll!System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(System.IntPtr dwComponentID, int reason, int pvLoopData) + 0x287 bytes System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(int reason, System.Windows.Forms.ApplicationContext context) + 0x16c bytes System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoop(int reason, System.Windows.Forms.ApplicationContext context) + 0x61 bytes System.Windows.Forms.dll!System.Windows.Forms.Application.Run(System.Windows.Forms.Form mainForm) + 0x31 bytes Tici.Kraps.Services.dll!Tici.Kraps.Services.Container.DefaultApplicationRunner.Run() Line 41 + 0x17 bytes C# Kraps.exe!Tici.Kraps.Program.Main() Line 105 + 0x9 bytes C# [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.AppDomain.ExecuteAssembly(string assemblyFile, System.Security.Policy.Evidence assemblySecurity, string[] args) + 0x6d bytes Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() + 0x2a bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x63 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool ignoreSyncCtx) + 0xb0 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x2c bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes [Native to Managed Transition]

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• I don't get prices with Amazon Product Advertising API

  - by Xarem

  I try to get prices of an ASIN number with the Amazon Product Advertising API. Code: $artNr = "B003TKSD8E"; $base_url = "http://ecs.amazonaws.de/onca/xml"; $params = array( 'AWSAccessKeyId' => self::API_KEY, 'AssociateTag' => self::API_ASSOCIATE_TAG, 'Version' => "2010-11-01", 'Operation' => "ItemLookup", 'Service' => "AWSECommerceService", 'Condition' => "All", 'IdType' => 'ASIN', 'ItemId' => $artNr); $params['Timestamp'] = gmdate("Y-m-d\TH:i:s.\\0\\0\\0\\Z", time()); $url_parts = array(); foreach(array_keys($params) as $key) $url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key])); sort($url_parts); $url_string = implode("&", $url_parts); $string_to_sign = "GET\necs.amazonaws.de\n/onca/xml\n" . $url_string; $signature = hash_hmac("sha256", $string_to_sign, self::API_SECRET, TRUE); $signature = urlencode(base64_encode($signature)); $url = $base_url . '?' . $url_string . "&Signature=" . $signature; $response = file_get_contents($url); $parsed_xml = simplexml_load_string($response); I think this should be correct - but I don't get offers in the response: SimpleXMLElement Object ( [OperationRequest] => SimpleXMLElement Object ( [RequestId] => ************************* [Arguments] => SimpleXMLElement Object ( [Argument] => Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Condition [Value] => All ) ) [1] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Operation [Value] => ItemLookup ) ) [2] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Service [Value] => AWSECommerceService ) ) [3] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => ItemId [Value] => B003TKSD8E ) ) [4] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => IdType [Value] => ASIN ) ) [5] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AWSAccessKeyId [Value] => ************************* ) ) [6] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Timestamp [Value] => 2011-11-29T01:32:12.000Z ) ) [7] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Signature [Value] => ************************* ) ) [8] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AssociateTag [Value] => ************************* ) ) [9] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Version [Value] => 2010-11-01 ) ) ) ) [RequestProcessingTime] => 0.0091540000000000 ) [Items] => SimpleXMLElement Object ( [Request] => SimpleXMLElement Object ( [IsValid] => True [ItemLookupRequest] => SimpleXMLElement Object ( [Condition] => All [IdType] => ASIN [ItemId] => B003TKSD8E [ResponseGroup] => Small [VariationPage] => All ) ) [Item] => SimpleXMLElement Object ( [ASIN] => B003TKSD8E [DetailPageURL] => http://www.amazon.de/Apple-iPhone-4-32GB-schwarz/dp/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB003TKSD8E [ItemLinks] => SimpleXMLElement Object ( [ItemLink] => Array ( [0] => SimpleXMLElement Object ( [Description] => Add To Wishlist [URL] => http://www.amazon.de/gp/registry/wishlist/add-item.html%3Fasin.0%3DB003TKSD8E%26SubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [1] => SimpleXMLElement Object ( [Description] => Tell A Friend [URL] => http://www.amazon.de/gp/pdp/taf/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [2] => SimpleXMLElement Object ( [Description] => All Customer Reviews [URL] => http://www.amazon.de/review/product/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [3] => SimpleXMLElement Object ( [Description] => All Offers [URL] => http://www.amazon.de/gp/offer-listing/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) ) ) [ItemAttributes] => SimpleXMLElement Object ( [Manufacturer] => Apple Computer [ProductGroup] => CE [Title] => Apple iPhone 4 32GB schwarz ) ) ) ) Can someone please explain me why I don't get any price-information? Thank you very much

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• How to get javascript object references or reference count?

  - by Tauren

  How to get reference count for an object Is it possible to determine if a javascript object has multiple references to it? Or if it has references besides the one I'm accessing it with? Or even just to get the reference count itself? Can I find this information from javascript itself, or will I need to keep track of my own reference counters. Obviously, there must be at least one reference to it for my code access the object. But what I want to know is if there are any other references to it, or if my code is the only place it is accessed. I'd like to be able to delete the object if nothing else is referencing it. If you know the answer, there is no need to read the rest of this question. Below is just an example to make things more clear. Use Case In my application, I have a Repository object instance called contacts that contains an array of ALL my contacts. There are also multiple Collection object instances, such as friends collection and a coworkers collection. Each collection contains an array with a different set of items from the contacts Repository. Sample Code To make this concept more concrete, consider the code below. Each instance of the Repository object contains a list of all items of a particular type. You might have a repository of Contacts and a separate repository of Events. To keep it simple, you can just get, add, and remove items, and add many via the constructor. var Repository = function(items) { this.items = items || []; } Repository.prototype.get = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { return this.items[i]; } } } Repository.prototype.add = function(item) { if (toString.call(item) === "[object Array]") { this.items.concat(item); } else { this.items.push(item); } } Repository.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { this.removeIndex(i); } } } Repository.prototype.removeIndex = function(index) { if (items[index]) { if (/* items[i] has more than 1 reference to it */) { // Only remove item from repository if nothing else references it this.items.splice(index,1); return; } } } Note the line in remove with the comment. I only want to remove the item from my master repository of objects if no other objects have a reference to the item. Here's Collection: var Collection = function(repo,items) { this.repo = repo; this.items = items || []; } Collection.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { // Remove object from this collection this.items.splice(i,1); // Tell repo to remove it (only if no other references to it) repo.removeIndxe(i); return; } } } And then this code uses Repository and Collection: var contactRepo = new Repository([ {id: 1, name: "Joe"}, {id: 2, name: "Jane"}, {id: 3, name: "Tom"}, {id: 4, name: "Jack"}, {id: 5, name: "Sue"} ]); var friends = new Collection( contactRepo, [ contactRepo.get(2), contactRepo.get(4) ] ); var coworkers = new Collection( contactRepo, [ contactRepo.get(1), contactRepo.get(2), contactRepo.get(5) ] ); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 2, 5 coworkers.remove(2); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 5 friends.remove(4); contactRepo.items; // contains item ids 1, 2, 3, 5 friends.items; // contains item ids 2 coworkers.items; // contains item ids 1, 5 Notice how coworkers.remove(2) didn't remove id 2 from contactRepo? This is because it was still referenced from friends.items. However, friends.remove(4) causes id 4 to be removed from contactRepo, because no other collection is referring to it. Summary The above is what I want to do. I'm sure there are ways I can do this by keeping track of my own reference counters and such. But if there is a way to do it using javascript's built-in reference management, I'd like to hear about how to use it.

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• How to implement Cocoa copyWithZone on derived object in MonoMac C#?

  - by Justin Aquadro

  I'm currently porting a small Winforms-based .NET application to use a native Mac front-end with MonoMac. The application has a TreeControl with icons and text, which does not exist out of the box in Cocoa. So far, I've ported almost all of the ImageAndTextCell code in Apple's DragNDrop example: https://developer.apple.com/library/mac/#samplecode/DragNDropOutlineView/Listings/ImageAndTextCell_m.html#//apple_ref/doc/uid/DTS40008831-ImageAndTextCell_m-DontLinkElementID_6, which is assigned to an NSOutlineView as a custom cell. It seems to be working almost perfectly, except that I have not figured out how to properly port the copyWithZone method. Unfortunately, this means the internal copies that NSOutlineView is making do not have the image field, and it leads to the images briefly vanishing during expand and collapse operations. The objective-c code in question is: - (id)copyWithZone:(NSZone *)zone { ImageAndTextCell *cell = (ImageAndTextCell *)[super copyWithZone:zone]; // The image ivar will be directly copied; we need to retain or copy it. cell->image = [image retain]; return cell; } The first line is what's tripping me up, as MonoMac does not expose a copyWithZone method, and I don't know how to otherwise call it. Update Based on current answers and additional research and testing, I've come up with a variety of models for copying an object. static List<ImageAndTextCell> _refPool = new List<ImageAndTextCell>(); // Method 1 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 2 [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); return cell; } [Export("dealloc")] public void Dealloc () { _refPool.Remove(this); this.Dispose(); } // Method 3 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 4 static IntPtr selRetain = Selector.GetHandle ("retain"); static IntPtr selRetainCount = Selector.GetHandle("retainCount"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone (IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell () { Title = Title, Image = Image, }; _refPool.Add (cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } public void PeriodicCleanup () { List<ImageAndTextCell> markedForDelete = new List<ImageAndTextCell> (); foreach (ImageAndTextCell cell in _refPool) { uint count = Messaging.UInt32_objc_msgSend (cell.Handle, selRetainCount); if (count == 1) markedForDelete.Add (cell); } foreach (ImageAndTextCell cell in markedForDelete) { _refPool.Remove (cell); cell.Dispose (); } } // Method 5 static IntPtr selCopyWithZone = Selector.GetHandle("copyWithZone:"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { IntPtr copyHandle = Messaging.IntPtr_objc_msgSendSuper_IntPtr(SuperHandle, selCopyWithZone, zone); ImageAndTextCell cell = new ImageAndTextCell(copyHandle) { Image = Image, }; _refPool.Add(cell); return cell; } Method 1: Increases the retain count of the unmanaged object. The unmanaged object will persist persist forever (I think? dealloc never called), and the managed object will be harvested early. Seems to be lose-lose all-around, but runs in practice. Method 2: Saves a reference of the managed object. The unmanaged object is left alone, and dealloc appears to be invoked at a reasonable time by the caller. At this point the managed object is released and disposed. This seems reasonable, but on the downside the base type's dealloc won't be run (I think?) Method 3: Increases the retain count and saves a reference. Unmanaged and managed objects leak forever. Method 4: Extends Method 3 by adding a cleanup function that is run periodically (e.g. during Init of each new ImageAndTextCell object). The cleanup function checks the retain counts of the stored objects. A retain count of 1 means the caller has released it, so we should as well. Should eliminate leaking in theory. Method 5: Attempt to invoke the copyWithZone method on the base type, and then construct a new ImageAndTextView object with the resulting handle. Seems to do the right thing (the base data is cloned). Internally, NSObject bumps the retain count on objects constructed like this, so we also use the PeriodicCleanup function to release these objects when they're no longer used. Based on the above, I believe Method 5 is the best approach since it should be the only one that results in a truly correct copy of the base type data, but I don't know if the approach is inherently dangerous (I am also making some assumptions about the underlying implementation of NSObject). So far nothing bad has happened "yet", but if anyone is able to vet my analysis then I would be more confident going forward.

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• A Communication System for XAML Applications

  - by psheriff

  In any application, you want to keep the coupling between any two or more objects as loose as possible. Coupling happens when one class contains a property that is used in another class, or uses another class in one of its methods. If you have this situation, then this is called strong or tight coupling. One popular design pattern to help with keeping objects loosely coupled is called the Mediator design pattern. The basics of this pattern are very simple; avoid one object directly talking to another object, and instead use another class to mediate between the two. As with most of my blog posts, the purpose is to introduce you to a simple approach to using a message broker, not all of the fine details. IPDSAMessageBroker Interface As with most implementations of a design pattern, you typically start with an interface or an abstract base class. In this particular instance, an Interface will work just fine. The interface for our Message Broker class just contains a single method “SendMessage” and one event “MessageReceived”. public delegate void MessageReceivedEventHandler( object sender, PDSAMessageBrokerEventArgs e); public interface IPDSAMessageBroker{  void SendMessage(PDSAMessageBrokerMessage msg);   event MessageReceivedEventHandler MessageReceived;} PDSAMessageBrokerMessage Class As you can see in the interface, the SendMessage method requires a type of PDSAMessageBrokerMessage to be passed to it. This class simply has a MessageName which is a ‘string’ type and a MessageBody property which is of the type ‘object’ so you can pass whatever you want in the body. You might pass a string in the body, or a complete Customer object. The MessageName property will help the receiver of the message know what is in the MessageBody property. public class PDSAMessageBrokerMessage{  public PDSAMessageBrokerMessage()  {  }   public PDSAMessageBrokerMessage(string name, object body)  {    MessageName = name;    MessageBody = body;  }   public string MessageName { get; set; }   public object MessageBody { get; set; }} PDSAMessageBrokerEventArgs Class As our message broker class will be raising an event that others can respond to, it is a good idea to create your own event argument class. This class will inherit from the System.EventArgs class and add a couple of additional properties. The properties are the MessageName and Message. The MessageName property is simply a string value. The Message property is a type of a PDSAMessageBrokerMessage class. public class PDSAMessageBrokerEventArgs : EventArgs{  public PDSAMessageBrokerEventArgs()  {  }   public PDSAMessageBrokerEventArgs(string name,     PDSAMessageBrokerMessage msg)  {    MessageName = name;    Message = msg;  }   public string MessageName { get; set; }   public PDSAMessageBrokerMessage Message { get; set; }} PDSAMessageBroker Class Now that you have an interface class and a class to pass a message through an event, it is time to create your actual PDSAMessageBroker class. This class implements the SendMessage method and will also create the event handler for the delegate created in your Interface. public class PDSAMessageBroker : IPDSAMessageBroker{  public void SendMessage(PDSAMessageBrokerMessage msg)  {    PDSAMessageBrokerEventArgs args;     args = new PDSAMessageBrokerEventArgs(      msg.MessageName, msg);     RaiseMessageReceived(args);  }   public event MessageReceivedEventHandler MessageReceived;   protected void RaiseMessageReceived(    PDSAMessageBrokerEventArgs e)  {    if (null != MessageReceived)      MessageReceived(this, e);  }} The SendMessage method will take a PDSAMessageBrokerMessage object as an argument. It then creates an instance of a PDSAMessageBrokerEventArgs class, passing to the constructor two items: the MessageName from the PDSAMessageBrokerMessage object and also the object itself. It may seem a little redundant to pass in the message name when that same message name is part of the message, but it does make consuming the event and checking for the message name a little cleaner – as you will see in the next section. Create a Global Message Broker In your WPF application, create an instance of this message broker class in the App class located in the App.xaml file. Create a public property in the App class and create a new instance of that class in the OnStartUp event procedure as shown in the following code: public partial class App : Application{  public PDSAMessageBroker MessageBroker { get; set; }   protected override void OnStartup(StartupEventArgs e)  {    base.OnStartup(e);     MessageBroker = new PDSAMessageBroker();  }} Sending and Receiving Messages Let’s assume you have a user control that you load into a control on your main window and you want to send a message from that user control to the main window. You might have the main window display a message box, or put a string into a status bar as shown in Figure 1. Figure 1: The main window can receive and send messages The first thing you do in the main window is to hook up an event procedure to the MessageReceived event of the global message broker. This is done in the constructor of the main window: public MainWindow(){  InitializeComponent();   (Application.Current as App).MessageBroker.     MessageReceived += new MessageReceivedEventHandler(       MessageBroker_MessageReceived);} One piece of code you might not be familiar with is accessing a property defined in the App class of your XAML application. Within the App.Xaml file is a class named App that inherits from the Application object. You access the global instance of this App class by using Application.Current. You cast Application.Current to ‘App’ prior to accessing any of the public properties or methods you defined in the App class. Thus, the code (Application.Current as App).MessageBroker, allows you to get at the MessageBroker property defined in the App class. In the MessageReceived event procedure in the main window (shown below) you can now check to see if the MessageName property of the PDSAMessageBrokerEventArgs is equal to “StatusBar” and if it is, then display the message body into the status bar text block control. void MessageBroker_MessageReceived(object sender,   PDSAMessageBrokerEventArgs e){  switch (e.MessageName)  {    case "StatusBar":      tbStatus.Text = e.Message.MessageBody.ToString();      break;  }} In the Page 1 user control’s Loaded event procedure you will send the message “StatusBar” through the global message broker to any listener using the following code: private void UserControl_Loaded(object sender,  RoutedEventArgs e){  // Send Status Message  (Application.Current as App).MessageBroker.    SendMessage(new PDSAMessageBrokerMessage("StatusBar",      "This is Page 1"));} Since the main window is listening for the message ‘StatusBar’, it will display the value “This is Page 1” in the status bar at the bottom of the main window. Sending a Message to a User Control The previous example sent a message from the user control to the main window. You can also send messages from the main window to any listener as well. Remember that the global message broker is really just a broadcaster to anyone who has hooked into the MessageReceived event. In the constructor of the user control named ucPage1 you can hook into the global message broker’s MessageReceived event. You can then listen for any messages that are sent to this control by using a similar switch-case structure like that in the main window. public ucPage1(){  InitializeComponent();   // Hook to the Global Message Broker  (Application.Current as App).MessageBroker.    MessageReceived += new MessageReceivedEventHandler(      MessageBroker_MessageReceived);} void MessageBroker_MessageReceived(object sender,  PDSAMessageBrokerEventArgs e){  // Look for messages intended for Page 1  switch (e.MessageName)  {    case "ForPage1":      MessageBox.Show(e.Message.MessageBody.ToString());      break;  }} Once the ucPage1 user control has been loaded into the main window you can then send a message using the following code: private void btnSendToPage1_Click(object sender,  RoutedEventArgs e){  PDSAMessageBrokerMessage arg =     new PDSAMessageBrokerMessage();   arg.MessageName = "ForPage1";  arg.MessageBody = "Message For Page 1";   // Send a message to Page 1  (Application.Current as App).MessageBroker.SendMessage(arg);} Since the MessageName matches what is in the ucPage1 MessageReceived event procedure, ucPage1 can do anything in response to that event. It is important to note that when the message gets sent it is sent to all MessageReceived event procedures, not just the one that is looking for a message called “ForPage1”. If the user control ucPage1 is not loaded and this message is broadcast, but no other code is listening for it, then it is simply ignored. Remove Event Handler In each class where you add an event handler to the MessageReceived event you need to make sure to remove those event handlers when you are done. Failure to do so can cause a strong reference to the class and thus not allow that object to be garbage collected. In each of your user control’s make sure in the Unloaded event to remove the event handler. private void UserControl_Unloaded(object sender, RoutedEventArgs e){  if (_MessageBroker != null)    _MessageBroker.MessageReceived -=         _MessageBroker_MessageReceived;} Problems with Message Brokering As with most “global” classes or classes that hook up events to other classes, garbage collection is something you need to consider. Just the simple act of hooking up an event procedure to a global event handler creates a reference between your user control and the message broker in the App class. This means that even when your user control is removed from your UI, the class will still be in memory because of the reference to the message broker. This can cause messages to still being handled even though the UI is not being displayed. It is up to you to make sure you remove those event handlers as discussed in the previous section. If you don’t, then the garbage collector cannot release those objects. Instead of using events to send messages from one object to another you might consider registering your objects with a central message broker. This message broker now becomes a collection class into which you pass an object and what messages that object wishes to receive. You do end up with the same problem however. You have to un-register your objects; otherwise they still stay in memory. To alleviate this problem you can look into using the WeakReference class as a method to store your objects so they can be garbage collected if need be. Discussing Weak References is beyond the scope of this post, but you can look this up on the web. Summary In this blog post you learned how to create a simple message broker system that will allow you to send messages from one object to another without having to reference objects directly. This does reduce the coupling between objects in your application. You do need to remember to get rid of any event handlers prior to your objects going out of scope or you run the risk of having memory leaks and events being called even though you can no longer access the object that is responding to that event. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A Communication System for XAML Applications” from the drop down list.

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• Metro: Understanding Observables

  - by Stephen.Walther

  The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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• Should pathfinder in A* hold closedSet and openedSet or each object should hold its sets?

  - by Patryk

  I am about to implement A* pathfinding algorithm and I wonder how should I implement this - from the point of view of architecture. I have the pathfinder as a class - I think I will instantiate only one object of this class (or maybe make it a Singleton - this is not so important). The hardest part for me is whether the closedSet and openedSet should be attached to objects that can find the path for them or should be stored in pathfinder class ? I am opened to any hints and critique whatsoever. What is the best practice considering pathfinding in terms of design ?

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• How to structure game states in an entity/component-based system

  - by Eva

  I'm making a game designed with the entity-component paradigm that uses systems to communicate between components as explained here. I've reached the point in my development that I need to add game states (such as paused, playing, level start, round start, game over, etc.), but I'm not sure how to do it with my framework. I've looked at this code example on game states which everyone seems to reference, but I don't think it fits with my framework. It seems to have each state handling its own drawing and updating. My framework has a SystemManager that handles all the updating using systems. For example, here's my RenderingSystem class: public class RenderingSystem extends GameSystem { private GameView gameView_; /** * Constructor * Creates a new RenderingSystem. * @param gameManager The game manager. Used to get the game components. */ public RenderingSystem(GameManager gameManager) { super(gameManager); } /** * Method: registerGameView * Registers gameView into the RenderingSystem. * @param gameView The game view registered. */ public void registerGameView(GameView gameView) { gameView_ = gameView; } /** * Method: triggerRender * Adds a repaint call to the event queue for the dirty rectangle. */ public void triggerRender() { Rectangle dirtyRect = new Rectangle(); for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); dirtyRect.add(graphicsComponent.getDirtyRect()); } gameView_.repaint(dirtyRect); } /** * Method: renderGameView * Renders the game objects onto the game view. * @param g The graphics object that draws the game objects. */ public void renderGameView(Graphics g) { for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); if (!graphicsComponent.isVisible()) continue; GraphicsComponent.Shape shape = graphicsComponent.getShape(); BoundsComponent boundsComponent = object.getComponent(BoundsComponent.class); Rectangle bounds = boundsComponent.getBounds(); g.setColor(graphicsComponent.getColor()); if (shape == GraphicsComponent.Shape.RECTANGULAR) { g.fill3DRect(bounds.x, bounds.y, bounds.width, bounds.height, true); } else if (shape == GraphicsComponent.Shape.CIRCULAR) { g.fillOval(bounds.x, bounds.y, bounds.width, bounds.height); } } } /** * Method: getRenderableObjects * @return The renderable game objects. */ private HashSet<GameObject> getRenderableObjects() { return gameManager.getGameObjectManager().getRelevantObjects( getClass()); } } Also all the updating in my game is event-driven. I don't have a loop like theirs that simply updates everything at the same time. I like my framework because it makes it easy to add new GameObjects, but doesn't have the problems some component-based designs encounter when communicating between components. I would hate to chuck it just to get pause to work. Is there a way I can add game states to my game without removing the entity-component design? Does the game state example actually fit my framework, and I'm just missing something? EDIT: I might not have explained my framework well enough. My components are just data. If I was coding in C++, they'd probably be structs. Here's an example of one: public class BoundsComponent implements GameComponent { /** * The position of the game object. */ private Point pos_; /** * The size of the game object. */ private Dimension size_; /** * Constructor * Creates a new BoundsComponent for a game object with initial position * initialPos and initial size initialSize. The position and size combine * to make up the bounds. * @param initialPos The initial position of the game object. * @param initialSize The initial size of the game object. */ public BoundsComponent(Point initialPos, Dimension initialSize) { pos_ = initialPos; size_ = initialSize; } /** * Method: getBounds * @return The bounds of the game object. */ public Rectangle getBounds() { return new Rectangle(pos_, size_); } /** * Method: setPos * Sets the position of the game object to newPos. * @param newPos The value to which the position of the game object is * set. */ public void setPos(Point newPos) { pos_ = newPos; } } My components do not communicate with each other. Systems handle inter-component communication. My systems also do not communicate with each other. They have separate functionality and can easily be kept separate. The MovementSystem doesn't need to know what the RenderingSystem is rendering to move the game objects correctly; it just need to set the right values on the components, so that when the RenderingSystem renders the game objects, it has accurate data. The game state could not be a system, because it needs to interact with the systems rather than the components. It's not setting data; it's determining which functions need to be called. A GameStateComponent wouldn't make sense because all the game objects share one game state. Components are what make up objects and each one is different for each different object. For example, the game objects cannot have the same bounds. They can have overlapping bounds, but if they share a BoundsComponent, they're really the same object. Hopefully, this explanation makes my framework less confusing.

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• How do I resolve "No JSON object could be decoded" on mythbuntu live CD?

  - by Neil

  I have been running a MythTV frontend on my laptop for some time against a MythTV backend installed in Linux Mint 12 on another computer, and everything works fine. Now, I'm trying out the Mythbuntu Live CD (12.04.1 32-bit) on the laptop, to turn it into a dedicated front end. It's connecting to the network just fine, and I can see my server. When I click on the frontend icon on the desktop, it asks me for the security code, which I've verified against mythtv-setup on the server. However, when I test that code, it shows the error message "No JSON object could be decoded". I've looked in the control center to see if there's something else I should be setting up. The message above implies to me that it can't find the server, but I can find no place in the control center to tell it where to find my myth backend, which I find a little odd. Does the live CD not work against a backend server on another machine?

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• UML class diagram - can aggregated object be part of two aggregated classes?

  - by user970696

  Some sources say that aggregation means that the class owns the object and shares reference. Lets assume an example where a company class holds a list of cars but departments of that company has list of cars used by them. class Department { list<Car> listOfCars; } class Company { list<Car> listOfCars; //initialization of the list } So in UML class diagram, I would do it like this. But I assume this is not allowed because it would imply that both company and department own the objects.. [COMPANY]<>------[CAR] [DEPARTMENT]<>---| //imagine this goes up to the car class

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• Collision Resolution

  - by ultifinitus

  Hey all, I'm making a simple side-scrolling game, and I would appreciate some input! My collision detection system is a simple bounding box detection, so it's really easy to implement. However my collision resolution is ridiculous! Currently I have a little formula like this: if (colliding(firstObject,secondObject)) firstObject.resolve_collision(yAxisOffset); if (colliding(firstObject,secondObject)) firstObject.resolve_collision(xAxisOffset); where yAxisOffset is only set if the first object's previous y position was outside the second object's collision frame, respectively xAxisOffset as well. Now this is working great, in general. However there is a single problem. When I have a stack of objects and I push the first object against that stack, the first object get's "stuck," on the stack. What's I think is happening is the object's collision system checks and resolves for collisions based on creation time, so If I check one axis, then the other, the object will "sink" object directly along the checking axis. This sinking action causes the collision detection routine to think there's a gap between our position and the other object's position, and when I finally check the object that I've already sunk into, my object's position is resolved to it's original position... All this is great, and I'm sure if I bang my head against a wall long enough i'll come up with a working algorithm, but I'd rather not =). So what in the heck do you think I should do? How could I change my collision resolution system to fix this? Here's the program (temporary link, not sure how long it'll last) (notes: arrow keys to navigate, click to drop block, x to jump) I'd appreciate any help you can offer!

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• Making a perfect map (not tile-based)

  - by Sri Harsha Chilakapati

  I would like to make a map system as in the GameMaker and the latest code is here. I've searched a lot in google and all of them resulted in tutorials about tile-maps. As tile maps do not fit for every type of game and GameMaker uses tiles for a different purpose, I want to make a "Sprite Based" map. The major problem I had experienced was collision detection being slow for large maps. So I wrote a QuadTree class here and the collision detection is fine upto 50000 objects in the map without PixelPerfect collision detection and 30000 objects with PixelPerferct collisions enabled. Now I need to implement the method "isObjectCollisionFree(float x, float y, boolean solid, GObject obj)". The existing implementation is becoming slow in Platformer games and I need suggestions on improvement. The current Implementation: /** * Checks if a specific position is collision free in the map. * * @param x The x-position of the object * @param y The y-position of the object * @param solid Whether to check only for solid object * @param object The object ( used for width and height ) * @return True if no-collision and false if it collides. */ public static boolean isObjectCollisionFree(float x, float y, boolean solid, GObject object){ boolean bool = true; Rectangle bounds = new Rectangle(Math.round(x), Math.round(y), object.getWidth(), object.getHeight()); ArrayList<GObject> collidables = quad.retrieve(bounds); for (int i=0; i<collidables.size(); i++){ GObject obj = collidables.get(i); if (obj.isSolid()==solid && obj != object){ if (obj.isAlive()){ if (bounds.intersects(obj.getBounds())){ bool = false; if (Global.USE_PIXELPERFECT_COLLISION){ bool = !GUtil.isPixelPerfectCollision(x, y, object.getAnimation().getBufferedImage(), obj.getX(), obj.getY(), obj.getAnimation().getBufferedImage()); } break; } } } } return bool; } Thanks.

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• Caching factory design

  - by max

  I have a factory class XFactory that creates objects of class X. Instances of X are very large, so the main purpose of the factory is to cache them, as transparently to the client code as possible. Objects of class X are immutable, so the following code seems reasonable: # module xfactory.py import x class XFactory: _registry = {} def get_x(self, arg1, arg2, use_cache = True): if use_cache: hash_id = hash((arg1, arg2)) if hash_id in _registry: return _registry[hash_id] obj = x.X(arg1, arg2) _registry[hash_id] = obj return obj # module x.py class X: # ... Is it a good pattern? (I know it's not the actual Factory Pattern.) Is there anything I should change? Now, I find that sometimes I want to cache X objects to disk. I'll use pickle for that purpose, and store as values in the _registry the filenames of the pickled objects instead of references to the objects. Of course, _registry itself would have to be stored persistently (perhaps in a pickle file of its own, in a text file, in a database, or simply by giving pickle files the filenames that contain hash_id). Except now the validity of the cached object depends not only on the parameters passed to get_x(), but also on the version of the code that created these objects. Strictly speaking, even a memory-cached object could become invalid if someone modifies x.py or any of its dependencies, and reloads it while the program is running. So far I ignored this danger since it seems unlikely for my application. But I certainly cannot ignore it when my objects are cached to persistent storage. What can I do? I suppose I could make the hash_id more robust by calculating hash of a tuple that contains arguments arg1 and arg2, as well as the filename and last modified date for x.py and every module and data file that it (recursively) depends on. To help delete cache files that won't ever be useful again, I'd add to the _registry the unhashed representation of the modified dates for each record. But even this solution isn't 100% safe since theoretically someone might load a module dynamically, and I wouldn't know about it from statically analyzing the source code. If I go all out and assume every file in the project is a dependency, the mechanism will still break if some module grabs data from an external website, etc.). In addition, the frequency of changes in x.py and its dependencies is quite high, leading to heavy cache invalidation. Thus, I figured I might as well give up some safety, and only invalidate the cache only when there is an obvious mismatch. This means that class X would have a class-level cache validation identifier that should be changed whenever the developer believes a change happened that should invalidate the cache. (With multiple developers, a separate invalidation identifier is required for each.) This identifier is hashed along with arg1 and arg2 and becomes part of the hash keys stored in _registry. Since developers may forget to update the validation identifier or not realize that they invalidated existing cache, it would seem better to add another validation mechanism: class X can have a method that returns all the known "traits" of X. For instance, if X is a table, I might add the names of all the columns. The hash calculation will include the traits as well. I can write this code, but I am afraid that I'm missing something important; and I'm also wondering if perhaps there's a framework or package that can do all of this stuff already. Ideally, I'd like to combine in-memory and disk-based caching.

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• From where does the game engines add location of an object?

  - by Player

  I have started making my first game( a pong game )with ruby (Gosu). I'm trying to detect the collision of two images using their location by comparing the location of the object (a ball) to another one(a player). For example: if (@player.x - @ball.x).abs <=184 && (@player.y - @ball.y).abs <= 40 @ball.vx = [email protected] @ball.vy = [email protected] But my problem is that with these numbers, the ball collides near the player sometimes, even though the dimensions of the player are correct. So my question is from where does the x values start to count? Is it from the center of gravity of the image or from the beginning of the image? (i.e When you add the image on a specific x,y,z what are these values compared to the image?

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• Design Pattern Books, Papers or Resources for Non-Object Orientated Paradigms?

  - by FinnNk

  After viewing this video on InfoQ about functional design patterns I was wondering what resources are out there on design patterns for non-object orientated paradigms. There are plenty out there for the OO world (GOF, etc, etc) and for architecture (EoEAA, etc, etc) but I'm not aware of what's out there for functional, logic, or other programming paradigms. Is there anything? A comment during the video suggests possibly not - does anyone know better? (By the way, by design patterns I don't mean language features or data structures but higher level approaches to designing an application - as discussed in the linked video)

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• Basic collision direction detection on 2d objects

  - by Osso Buko

  I am trying to develop a platform game for Android by using ANdroid GL Engine (ANGLE). And I am having trouble with collision detection. I have two objects which is shaped as rectangular. And no change in rotation. Here is a scheme of attributes of objects. What i am trying to do is when objects collide they block each other's movement on that direction. Every object has 4 boolean (bTop, bBottom, bRight, bLeft). For example when bBottom is true object can't advance on that direction. I came up with a solution but it seems it only works on one dimensional. Bottom and top or right and left. public void collisionPlatform (MyObject a, MyObject b) { // first obj is player and second is a wall or a platform Vector p1 = a.mPosition; // p1 = middle point of first object Vector d1 = a.mPosition2; // width(mX) and height of first object Vector mSpeed1 = a.mSpeed; // speed vector of first object Vector p2 = b.mPosition; // p1 = middle point of second object Vector d2 = b.mPosition2; // width(mX) and height of second object Vector mSpeed2 = b.mSpeed; // speed vector of second object float xDist, yDist; // distant between middle of two object float width , height; // this is average of two objects measurements width=(width1+width2)/2 xDist=(p1.mX - p2.mX); // calculate distance // if positive first object is at the right yDist=(p1.mY - p2.mY); // if positive first object is below width = d1.mX + d2.mX; // average measurements calculate height = d1.mY + d2.mY; width/=2; height/=2; if (Math.abs(xDist) < width && Math.abs(yDist) < height) { // Two object is collided if(p1.mY>p2.mY) { // first object is below second one a.bTop = true; if(a.mSpeed.mY<0) a.mSpeed.mY=0; b.bBottom = true; if(b.mSpeed.mY>0) b.mSpeed.mY=0; } else { a.bBottom = true; if(a.mSpeed.mY>0) a.mSpeed.mY=0; b.bTop = true; if(b.mSpeed.mY<0) b.mSpeed.mY=0; } } As seen in my code it simply will not work. when object comes from right or left it doesn't work. I tried couple of ways other than this one but none worked. I am guessing right method will include mSpeed vector. But I have no idea how to do it. I really appreciate if you could help. Sorry for my bad english.

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• How to design a game engine in an object-oriented language?

  - by chuzzum

  Whenever I try and write a game in any object-oriented language, the first problem I always face (after thinking about what kind of game to write) is how to design the engine. Even if I'm using existing libraries or frameworks like SDL, I still find myself having to make certain decisions for every game, like whether to use a state machine to manage menus, what kind of class to use for resource loading, etc. What is a good design and how would it be implemented? What are some tradeoffs that have to be made and their pros/cons?

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• How do you know when to split an object method into 2 or more other methods?

  - by blacktie24

  Hi, I know this is a very basic question, but I sometimes find myself struggling to figure out when to split a single object method into multiple methods. For example, I am trying to set up an ACL using Zend_Acl and Zend_Auth, as shown in this tutorial: http://devzone.zend.com/article/1665. However, I am wondering if the My_Plugin_Auth::preDispatch() method should invoke calls to a method called authenticate() and a method called authorize(), instead of having everything lumped in under preDispatch(). I was thinking that this would make the code more readable and encapsulate the logic into its smaller parts, but i'm not sure if this is reason enough.

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