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  • Can I make a derived class inherit a derived member from its base class in Java?

    - by Eric
    I have code that looks like this: public class A { public void doStuff() { System.out.print("Stuff successfully done"); } } public class B extends A { public void doStuff() { System.out.print("Stuff successfully done, but in a different way"); } public void doMoreStuff() { System.out.print("More advanced stuff successully done"); } } public class AWrapper { public A member; public AWrapper(A member) { this.member = member; } public void doStuffWithMember() { a.doStuff(); } } public class BWrapper extends AWrapper { public B member; public BWrapper(B member) { super(member); //Pointer to member stored in two places: this.member = member; //Not great if one changes, but the other does not } public void doStuffWithMember() { member.doMoreStuff(); } } However, there is a problem with this code. I'm storing a reference to the member in two places, but if one changes and the other does not, there could be trouble. I know that in Java, an inherited method can narrow down its return type (and perhaps arguments, but I'm not certain) to a derived class. Is the same true of fields?

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  • SQL 2008 R2 Named Instance Client Connectivity Issues?

    - by Jerry Dodge
    We're upgrading our software from using SQL 2000 to 2008 R2. Our customers will be installing an update which uninstalls 2000 and installs 2008 R2 under the same instance. So if no instance existed, then no instance name will be set (default). However, the problem starts with the customers which have a named SQL instance. Starting in 2008 R2 (not sure of ones before), for some reason, a client connecting to the server by its instance name is unsuccessful. I'm testing from the Management Studio - if I can't connect this, then nothing can connect. I browse network servers, and find the specific server\instance in the list. But, upon trying to connect to an instance name like MyServer\INST, I get: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) (Microsoft SQL Server, Error: -1) I do in fact have TCP/IP and Named Pipes protocols enabled, this is the first thing I did. When I connect to the server using a comma (,) and port number like MyServer, 49195, it works just fine. So it appears that client computers are just unable to identify the instance names. This has happened on all our installations of SQL 2008 R2 and from all client computers, including Win 7, XP, Vista, Server 2008, and Server 2003. We never experienced such issues on earlier versions of SQL. The problem even persists if the firewalls and antiviruses are all disabled. Now, this is a large update which we will be distributing soon to all our customers, and we want to minimize the interaction they need with us to get this installed. We absolutely hate the idea of using a port number, because it will always be different, and we would have to modify each client to point to this server/port. Some of our customers may have hundreds of client computers. How do I make client connections to a named SQL instance work again? After all, this is the whole purpose of named instances, and if a client can't connect to this instance by its name, then what is it even named for? EDIT It was mentioned to make sure SQL Browser is running, so I checked, and it is running. The server is also able to connect to its self (locally) - just external connections are refused. UPDATE After more careful checking, I learned the firewall wasn't completely disabled when testing, and upon disabling it completely, this works. So it appears that SQL Browser is being blocked by the firewall from external clients from accessing.

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  • What are the advantages of a query using a derived table(s) over a query not using them?

    - by AspOnMyNet
    I know how derived tables are used, but I still can’t really see any real advantages of using them. For example, in the following article http://techahead.wordpress.com/2007/10/01/sql-derived-tables/ the author tried to show benefits of a query using derived table over a query without one with an example, where we want to generate a report that shows off the total number of orders each customer placed in 1996, and we want this result set to include all customers, including those that didn’t place any orders that year and those that have never placed any orders at all( he’s using Northwind database ). But when I compare the two queries, I fail to see any advantages of a query using a derived table ( if nothing else, use of a derived table doesn't appear to simplify our code, at least not in this example): Regular query: SELECT C.CustomerID, C.CompanyName, COUNT(O.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN Orders O ON C.CustomerID = O.CustomerID AND YEAR(O.OrderDate) = 1996 GROUP BY C.CustomerID, C.CompanyName Query using a derived table: SELECT C.CustomerID, C.CompanyName, COUNT(dOrders.OrderID) AS TotalOrders FROM Customers C LEFT OUTER JOIN (SELECT * FROM Orders WHERE YEAR(Orders.OrderDate) = 1996) AS dOrders ON C.CustomerID = dOrders.CustomerID GROUP BY C.CustomerID, C.CompanyName Perhaps this just wasn’t a good example, so could you show me an example where benefits of derived table are more obvious? thanx

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  • Classes / instances in Ontology

    - by SODA
    Hi, I'm trying to comprehend ontology basics. Here's an example: car (class) 2009 VW CC (sub-class or instance?) My neighbor's 2009 VW CC (instance) My issue is understanding what is "2009 VW CC" (as a car model). If you're making product model a sub-class in the ontology - all of a sudden your ontology becomes bloated with thousands of subclasses of a "car". That's redundant. At the same time we can't say "2009 VW CC" is an instance, at least it's not material instance of a class. Does it make sense to distinguish between regular instances and material (distinct physical objects)? At the other hand, if both are instances (of different nature so to say), then how can instance inherit properties / relations of a non-class?

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  • Django comparing model instances for equality

    - by orokusaki
    I understand that, with a singleton situation, you can perform such an operation as: spam == eggs and if spam and eggs are instances of the same class with all the same attribute values, it will return True. In a Django model, this is natural because two separate instances of a model won't ever be the same unless they have the same .pk value. The problem with this is that if a reference to an instance has attributes that have been updated by middleware somewhere along the way and it hasn't been saved, and you're trying to it to another variable holding a reference to an instance of the same model, it will return False of course because they have different values for some of the attributes. Obviously I don't need something like a singleton , but I'm wondering if there some official Djangonic (ha, a new word) method for checking this, or if I should simply check that the .pk value is the same with: spam.pk == eggs.pk I'm sorry if this was a huge waste of time, but it just seems like there might be a method for doing this, and something I'm missing that I'll regret down the road if I don't find it.

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  • Raphael Scope Drag n drop multiple paper instances

    - by donald
    I have two Raphael paper instances. In both I want to drag and drop an element (circle). It is important for me to assign both these circles the same id. I expected no problem, as both are in different paper instances and therefore in different scope. What happens is, that somehow both elements react, when I have clicked both elements at least once. If I however give these elements different IDs everything works fine (each element only calls its "start", "drag" and "up" function if draged around). Is this intended behaviour of Raphael and do I have to assign different IDs to the elements in the different paper instances? Hopefully not and you can point me to the right direction :-) Thanks a lot for your Help in advance, Here comes the code: <!doctype html> <html> <head> <meta charset="utf-8" /> <title>DragNDrop</title> <script src="raphael-min.js"></script> </head> <body> <h1>Paper1</h1> <div id="divPaper1" style ="height: 150px; width: 300px; border:thin solid red"></div> <h1>Paper2</h1> <div id="divPaper2" style ="height: 150px; width: 300px; border:thin solid red"></div> <script> start1 = function () { console.log("start1"); } drag1 = function () { console.log("move1"); } up1 = function () { console.log("up1"); } start2 = function () { console.log("start2"); } drag2 = function () { console.log("move2"); } up2 = function () { console.log("up2"); } var paper1 = Raphael("divPaper1", "100%", "100%"); var circle1 = paper1.circle(40, 40, 30); circle1.attr("fill", "yellow"); circle1.id = "circle"; //both circles get the same id circle1.drag(drag1, start1, up1); paper2 = Raphael("divPaper2", "100%", "100%"); var circle2 = paper2.circle(40, 40, 30); circle2.attr("fill", "red"); circle2.id = "circle"; //both circles get the same id circle2.drag(drag2, start2, up2); </script> </body>

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  • Load two instances of the same DLL in Delphi

    - by Tom
    Here's my problem: I would like to create two separate instances of the same DLL. The following doesn't work because Handle1 and Handle2 will get the same address Handle1 := LoadLibrary('mydll.dll'); Handle2 := LoadLibrary('mydll.dll'); The following works, but I have to make a copy of the DLL and rename it to something else (which seems a bit silly) Handle1 := LoadLibrary('mydll.dll'); Handle2 := LoadLibrary('mydll2.dll'); Is there a way to have only one DLL file, but load several instances of it?

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  • WPF textbox derived control override drag&drop OnPreviewDrop (C sharp)

    - by Petr Klus
    Hi, I have been working on my custom control derived from the TextBox and I have encountered a problem I can not solve right now. Brief description of the problem: my textbox contains plain text which contains tags which I want to keep consistent - so far I have overriden text selection so they can be selected only as a whole tag etc. Right now I have moved to processing of drag&drop. If any text is dropped on the textfield and it is dropped on the tag, I want the insertion to be moved before or after the tag. The actual problem is with setting of the e.Handled=true. If I set it to true, it almost works - the text is inserted via my routine, but it is not removed from the source. If I set it to false, after executing my method the original textbox's insertion method is run. Is there any way to alter event routing? Or am I approaching this wrong from the start? Code of my method: protected override void OnPreviewDragEnter(DragEventArgs e) { base.OnPreviewDragEnter(e); e.Handled = true; // let us draw our very own caret... } protected override void OnPreviewDrop(DragEventArgs e) { base.OnPreviewDrop(e); fieldsReady = false; int selStart = this.SelectionStart; int selLength = this.SelectionLength; string droppedData = (string)e.Data.GetData(DataFormats.StringFormat); // where to insert Point whereDropped = e.GetPosition(this); int droppedIndex = GetCharacterIndexFromPoint(whereDropped, true); if (droppedIndex == this.Text.Length - 1) { double c = GetRectFromCharacterIndex(droppedIndex).X; if (whereDropped.X > c) droppedIndex++; } // only if the source was us, do this: if (this.SelectionLength > 0) // this means that we are dragging from our textbox! { // was there any selection? if so, remove it! this.Text = this.Text.Substring(0, selStart) + this.Text.Substring(selStart + selLength); e.Handled = true; // 2DO!! alter the indices depending on the removed selection // insertion this.Text = this.Text.Substring(0, droppedIndex) + droppedData + this.Text.Substring(droppedIndex); } }

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  • Load two instances of the same DLL in Delphi

    - by Tom
    Here's my problem: I would like to create two separate instances of the same DLL. The following doesn't work because Handle1 and Handle2 will get the same address Handle1 := LoadLibrary('mydll.dll'); Handle2 := LoadLibrary('mydll.dll'); The following works, but I have to make a copy of the DLL and rename it to something else (which seems a bit silly) Handle1 := LoadLibrary('mydll.dll'); Handle2 := LoadLibrary('mydll2.dll'); Is there a way to have only one DLL file, but load several instances of it?

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  • Objectify - Retrieve subclass instances with superclass query

    - by Deviling Master
    for a project i'm making, i'm using Objectify and Google AppEngine I'm quoting and old message from Google Groups, but the problem i have is the same: Here's the problem I'm trying to solve: I'd like to persist instances of several subclasses of one superclass to the datastore, and then retrieve them by querying for that superclass. (For example, a query for Game would return instances of Chess and Backgammon). Is there any way to accomplish this using Objectify? Because the thing i want is the same, but the topic does not provides yet an answer (it's 3 years old), I moved here with the same question. From 2010 to now, this question has been solved? Thanks Bye

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  • SSIS - user variable used in derived column transform is not available - in some cases

    - by soo
    Unfortunately I don't have a repro for my issue, but I thought I would try to describe it in case it sounds familiar to someone... I am using SSIS 2005, SP2. My package has a package-scope user variable - let's call it user_var first step in the control flow is an Execute SQL task which runs a stored procedure. All that SP does is insert a record in a SQL table (with an identity column) and then go back and get the max ID value. The Execute SQL task saves this output into user_var the control flow then has a Data Flow Task - it goes and gets some source data, has a derived column which sets a column called run_id to user_var - and saves the data to a SQL destination In most cases (this template is used for many packages, running every day) this all works great. All of the destination records created get set with a correct run_id. However, in some cases, there is a set of the destination data that does not get run_id equal to user_var, but instead gets a value of 0 (0 is the default value for user_var). I have 2 instances where this has happened, but I can't make it happen. In both cases, it was just less that 10,000 records that have run_id = 0. Since SSIS writes data out in 10,000 record blocks, this really makes me think that, for the first set of data written out, user_var was not yet set. Then, after that first block, for the rest of the data, run_id is set to a correct value. But control passed on to my data flow from the Execute SQL task - it would have seemed reasonable to me that it wouldn't go on until the SP has completed and user_var is set. Maybe it just runs the SP, but doesn't wait for it to complete? In both cases where this has happened there seemed to be a few packages hitting the table to get a new user_var at about the same time. And in both cases lots of data was written (40 million rows, 60 million rows) - my thinking is that that means the writes were happening for a while. Sorry to be both long-winded AND vague. A winning combination! Does this sound familiar to anyone? Thanks.

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  • Templated derived class in CRTP (Curiously Recurring Template Pattern)

    - by Butterwaffle
    Hi, I have a use of the CRTP that doesn't compile with g++ 4.2.1, perhaps because the derived class is itself a template? Does anyone know why this doesn't work or, better yet, how to make it work? Sample code and the compiler error are below. Source: foo.C #include <iostream> using namespace std; template<typename X, typename D> struct foo; template<typename X> struct bar : foo<X,bar<X> > { X evaluate() { return static_cast<X>( 5.3 ); } }; template<typename X> struct baz : foo<X,baz<X> > { X evaluate() { return static_cast<X>( "elk" ); } }; template<typename X, typename D> struct foo : D { X operator() () { return static_cast<D*>(this)->evaluate(); } }; template<typename X, typename D> void print_foo( foo<X,D> xyzzx ) { cout << "Foo is " << xyzzx() << "\n"; } int main() { bar<double> br; baz<const char*> bz; print_foo( br ); print_foo( bz ); return 0; } Compiler errors foo.C: In instantiation of ‘foo<double, bar<double> >’: foo.C:8: instantiated from ‘bar<double>’ foo.C:30: instantiated from here foo.C:18: error: invalid use of incomplete type ‘struct bar<double>’ foo.C:8: error: declaration of ‘struct bar<double>’ foo.C: In instantiation of ‘foo<const char*, baz<const char*> >’: foo.C:13: instantiated from ‘baz<const char*>’ foo.C:31: instantiated from here foo.C:18: error: invalid use of incomplete type ‘struct baz<const char*>’ foo.C:13: error: declaration of ‘struct baz<const char*>’

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  • Actionscript 3.0 Get all instances of a class?

    - by Windbrand
    I got a ton of movieclips in a class. Is there a more efficient way to apply a function to every instance in the class other than this? var textArray:Array = [ interludes.interludeIntro.interludeBegin1, interludes.interludeIntro.interludeBegin2, interludes.interludeIntro.interludeBegin3, interludes.interludeIntro.interludeBegin4, interludes.interludeIntro.interludeBegin5, interludes.interludeIntro.interludeBegin6, interludes.interludeIntro.interludeBegin7, //... ... ... interludes.interludeIntro.interludeBegin15 ]; for each (var interludeText:MovieClip in interludeBeginText) { interludeText.alpha = 0 //clear all text first } Also for some reason this doesn't work: interludes.interludeIntro.alpha = 0; It permanently turns that class invisible, even if I try to make specific instances visible later with: interludes.interludeIntro.interludeBegin1.alpha = 1; I have NO idea why the above doesn't work. I want to turn every single instance in the class interludeIntro invisible, but I want to turn specific instances visible later. (btw I have no idea how to insert code on this website, pressing "code" doesn't do anything, so pardon the bad formatting)

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  • How can I include my derived class type name in the serialized JSON?

    - by ChrisD
    Sometimes working with the js Serializer is easy, sometimes its not.   When I attempt to serialize an object that is derived from a base, the serializer decided whether or not to include the type name. When its present, the type name is represented by a ___type attribute in the serialized json like this: {"d":{"__type":"Commerce.Integration.Surfaces.OrderCreationRequest","RepId":0}} The missing type name is a problem if I intend to ship the object back into a web method that needs to deserialize the object.   Without the Type name, serialization will fail and result in a ugly web exception. The solution, which feels more like a work-around, is to explicitly tell the serializer to ALWAYS generate the type name for each derived type.  You make this declaration by adding a [GenerateScriptType())] attribute for each derived type to the top of the web page declaration.   For example, assuming I had 3 derivations of OrderCreationRequest; PersonalOrderCreationRequest, CompanyOrderCreationRequest, InternalOrderCreationRequestion, the code-behind for my web page would be decorated as follows: [GenerateScriptType(typeof(PersonalOrderCreationRequest))] [GenerateScriptType(typeof(CompanyOrderCreationRequest))] [GenerateScriptType(typeof(InternalOrderCreationRequest))] public partial class OrderMethods : Page { ... } With the type names generated in the serialized JSON, the serializer can successfully deserialize instances of any of these types passed into a web method. Hope this helps you as much as it did me.

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  • Model binding & derived model classes

    - by Richard Ev
    Does ASP.NET MVC offer any simple way to get model binding to work when you have model classes that inherit from others? In my scenario I have a View that is strongly typed to List<Person>. I have a couple of classes that inherit from Person, namely PersonTypeOne and PersonTypeTwo. I have three strongly typed partial views with names that match these class names (and render form elements for the properties of their respective models). This means that in my main View I can have the following code: <% for(int i = 0; i < Model.Count; i++) { Html.RenderPartial(Model[i].GetType().Name, Model[i]); } %> This works well, apart from when the user submits the form the relevant controller action method just gets a List<Person>, rather than a list of Person, PersonTypeOne and PersonTypeTwo. This is pretty much as expected as the form submission doesn't contain enough information to tell the default model binder to create any instances of PersonTypeOne and PersonTypeTwo classes. So, is there any way to get such functionality from the default model binder?

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  • using xml type attribute for derived complex types

    - by David Michel
    Hi All, I'm trying to get derived complex types from a base type in an xsd schema. it works well when I do this (inspired by this): xml file: <person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Employee"> <name>John</name> <height>59</height> <jobDescription>manager</jobDescription> </person> xsd file: <xs:element name="person" type="Person"/> <xs:complexType name="Person" abstract="true"> <xs:sequence> <xs:element name= "name" type="xs:string"/> <xs:element name= "height" type="xs:double" /> </xs:sequence> </xs:complexType> <xs:complexType name="Employee"> <xs:complexContent> <xs:extension base="Person"> <xs:sequence> <xs:element name="jobDescription" type="xs:string" /> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> However, if I want to have the person element inside, for example, a sequence of another complex type, it doesn't work anymore: xml: <staffRecord> <company>mycompany</company> <dpt>sales</dpt> <person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="Employee"> <name>John</name> <height>59</height> <jobDescription>manager</jobDescription> </person> </staffRecord> xsd file: <xs:element name="staffRecord"> <xs:complexType> <xs:sequence> <xs:element name="company" type="xs:string"/> <xs:element name="dpt" type="xs:string"/> <xs:element name="person" type="Person"/> <xs:complexType name="Person" abstract="true"> <xs:sequence> <xs:element name= "name" type="xs:string"/> <xs:element name= "height" type="xs:double" /> </xs:sequence> </xs:complexType> <xs:complexType name="Employee"> <xs:complexContent> <xs:extension base="Person"> <xs:sequence> <xs:element name="jobDescription" type="xs:string" /> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> </xs:sequence> </xs:complexType> </xs:element> When validating the xml with that schema with xmllint (under linux), I get this error message then: config.xsd:12: element complexType: Schemas parser error : Element '{http://www.w3.org/2001/XMLSchema}sequence': The content is not valid. Expected is (annotation?, (element | group | choice | sequence | any)*). WXS schema config.xsd failed to compile Any idea what is wrong ? David

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  • POCO inherited type could not pass addObject method

    - by bryanevil
    Hi all I am using a POCO class name "Company" generate from the T4 POCO code generator to create a derived class - name "CompanyBO" by "public class CompanyBO:Company", but when i call addObject method: public void Delete(T entity) { CustomerWebPortalEntities entities = new CustomerWebPortalEntities(); entities.AddObject(entity.GetType().BaseType.Name, entity); entities.DeleteObject(entity); SaveChanges(); } it compliant this: The EntitySet name 'CustomerWebPortalEntities.Company' could not be found. System.Data.Objects.ObjectContext.GetEntitySet(String entitySetName, String entityContainerName) at System.Data.Objects.ObjectContext.GetEntitySetFromName(String entitySetName) Could you please tell me whats going wrong here? How do I resolve this problem? Best Regards Bryan

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  • C# new class with only single property : derive from base or encapsulate into new ?

    - by Gobol
    I've tried to be descriptive :) It's rather programming-style problem than coding problem in itself. Let's suppose we have : A: public class MyDict { public Dictionary<int,string> dict; // do custom-serialization of "dict" public void SaveToFile(...); // customized deserialization of "dict" public void LoadFromFile(...); } B: public class MyDict : Dictionary<int,string> { } Which option would be better in the matter of programming style ? class B: is to be de/serialized externally. Main problem is : is it better to create new class (which would have only one property - like opt A:) or to create a new class derived - like opt B: ? I don't want any other data processing than adding/removing and de/serializing to stream. Thanks in advance!

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  • Why do I get an exception when playing multiple sound instances?

    - by Boreal
    Right now, I'm adding a rudimentary sound engine to my game. So far, I am able to load in a WAV file and play it once, then free up the memory when I close the game. However, the game crashes with a nice ArgumentOutOfBoundsException when I try to play another sound instance. Specified argument was out of the range of valid values. Parameter name: readLength I'm following this tutorial pretty much exactly, but I still keep getting the aforementioned error. Here's my sound-related code. /// <summary> /// Manages all sound instances. /// </summary> public static class Audio { static XAudio2 device; static MasteringVoice master; static List<SoundInstance> instances; /// <summary> /// The XAudio2 device. /// </summary> internal static XAudio2 Device { get { return device; } } /// <summary> /// Initializes the audio device and master track. /// </summary> internal static void Initialize() { device = new XAudio2(); master = new MasteringVoice(device); instances = new List<SoundInstance>(); } /// <summary> /// Releases all XA2 resources. /// </summary> internal static void Shutdown() { foreach(SoundInstance i in instances) i.Dispose(); master.Dispose(); device.Dispose(); } /// <summary> /// Registers a sound instance with the system. /// </summary> /// <param name="instance">Sound instance</param> internal static void AddInstance(SoundInstance instance) { instances.Add(instance); } /// <summary> /// Disposes any sound instance that has stopped playing. /// </summary> internal static void Update() { List<SoundInstance> temp = new List<SoundInstance>(instances); foreach(SoundInstance i in temp) if(!i.Playing) { i.Dispose(); instances.Remove(i); } } } /// <summary> /// Loads sounds from various files. /// </summary> internal class SoundLoader { /// <summary> /// Loads a .wav sound file. /// </summary> /// <param name="format">The decoded format will be sent here</param> /// <param name="buffer">The data will be sent here</param> /// <param name="soundName">The path to the WAV file</param> internal static void LoadWAV(out WaveFormat format, out AudioBuffer buffer, string soundName) { WaveStream wave = new WaveStream(soundName); format = wave.Format; buffer = new AudioBuffer(); buffer.AudioData = wave; buffer.AudioBytes = (int)wave.Length; buffer.Flags = BufferFlags.EndOfStream; } } /// <summary> /// Manages the data for a single sound. /// </summary> public class Sound : IAsset { WaveFormat format; AudioBuffer buffer; /// <summary> /// Loads a sound from a file. /// </summary> /// <param name="soundName">The path to the sound file</param> /// <returns>Whether the sound loaded successfully</returns> public bool Load(string soundName) { if(soundName.EndsWith(".wav")) SoundLoader.LoadWAV(out format, out buffer, soundName); else return false; return true; } /// <summary> /// Plays the sound. /// </summary> public void Play() { Audio.AddInstance(new SoundInstance(format, buffer)); } /// <summary> /// Unloads the sound from memory. /// </summary> public void Unload() { buffer.Dispose(); } } /// <summary> /// Manages a single sound instance. /// </summary> public class SoundInstance { SourceVoice source; bool playing; /// <summary> /// Whether the sound is currently playing. /// </summary> public bool Playing { get { return playing; } } /// <summary> /// Starts a new instance of a sound. /// </summary> /// <param name="format">Format of the sound</param> /// <param name="buffer">Buffer holding sound data</param> internal SoundInstance(WaveFormat format, AudioBuffer buffer) { source = new SourceVoice(Audio.Device, format); source.BufferEnd += (s, e) => playing = false; source.Start(); source.SubmitSourceBuffer(buffer); // THIS IS WHERE THE EXCEPTION IS THROWN playing = true; } /// <summary> /// Releases memory used by the instance. /// </summary> internal void Dispose() { source.Dispose(); } } The exception occurs on line 156 when I am playing the sound: source.SubmitSourceBuffer(buffer);

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  • OSGI Declarative Services (DS): What is a good way of using service component instances

    - by Christoph
    I am just getting started with OSGI and Declarative Services (DS) using Equinox and Eclipse PDE. I have 2 Bundles, A and B. Bundle A exposes a component which is consumed by Bundle B. Both bundles also expose this service to the OSGI Service registry again. Everything works fine so far and Equinox is wireing the components together, which means the Bundle A and Bundle B are instanciated by Equinox (by calling the default constructor) and then the wireing happens using the bind / unbind methods. Now, as Equinox is creating the instances of those components / services I would like to know what is the best way of getting this instance? So assume there is third class class which is NOT instantiated by OSGI: Class WantsToUseComponentB{ public void doSomethingWithComponentB(){ // how do I get componentB??? Something like this maybe? ComponentB component = (ComponentB)someComponentRegistry.getComponent(ComponentB.class.getName()); } I see the following options right now: 1. Use a ServiceTracker in the Activator to get the Service of ComponentBundleA.class.getName() (I have tried that already and it works, but it seems to much overhead to me) and make it available via a static factory methods public class Activator{ private static ServiceTracker componentBServiceTracker; public void start(BundleContext context){ componentBServiceTracker = new ServiceTracker(context, ComponentB.class.getName(),null); } public static ComponentB getComponentB(){ return (ComponentB)componentBServiceTracker.getService(); }; } 2. Create some kind of Registry where each component registers as soon as the activate() method is called. public ComponentB{ public void bind(ComponentA componentA){ someRegistry.registerComponent(this); } or public ComponentB{ public void activate(ComponentContext context){ someRegistry.registerComponent(this); } } } 3. Use an existing registry inside osgi / equinox which has those instances? I mean OSGI is already creating instances and wires them together, so it has the objects already somewhere. But where? How can I get them? Conclusion Where does the class WantsToUseComponentB (which is NOT a Component and NOT instantiated by OSGI) get an instance of ComponentB from? Are there any patterns or best practises? As I said I managed to use a ServiceTracker in the Activator, but I thought that would be possible without it. What I am looking for is actually something like the BeanContainer of Springframework, where I can just say something like Container.getBean(ComponentA.BEAN_NAME). But I don't want to use Spring DS. I hope that was clear enough. Otherwise I can also post some source code to explain in more detail. Thanks Christoph UPDATED: Answer to Neil's comment: Thanks for clarifying this question against the original version, but I think you still need to state why the third class cannot be created via something like DS. Hmm don't know. Maybe there is a way but I would need to refactor my whole framework to be based on DS, so that there are no "new MyThirdClass(arg1, arg2)" statements anymore. Don't really know how to do that, but I read something about ComponentFactories in DS. So instead of doing a MyThirdClass object = new MyThirdClass(arg1, arg2); I might do a ComponentFactory myThirdClassFactory = myThirdClassServiceTracker.getService(); // returns a if (myThirdClassFactory != null){ MyThirdClass object = objectFactory.newInstance(); object.setArg1("arg1"); object.setArg2("arg2"); } else{ // here I can assume that some service of ComponentA or B went away so MyThirdClass Componenent cannot be created as there are missing dependencies? } At the time of writing I don't know exactly how to use the ComponentFactories but this is supposed to be some kind of pseudo code :) Thanks Christoph

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  • Tomcat - virtualhosting - name / ip / port - based

    - by lisak
    Hey, what are the usage scenarios for these kinds of virtual hosting ? Name Based - typical tomcat virtual hosting, one HOME instance with many contexts, each as an individual host IP based / port based - multiple instances of tomcat ( how is it with performance and memory consuption?) running on IP aliases (virtual IPs) for one network adapter, usually behind http apache server that can run name based virtual hostings. Otherwise I can't figure out how would I forward requests in iptables/firewall based on IP address, which is just one. How is IP based virtual hosting done as to Tomcat and multiple instances ? I'd like to hear some usage scenarios from your experience. How are you running your applications. Cause there are applications having it's own modified classloader and they are developed in a way to run alone withing a tomcat instance. Then there are trivial applications which can run within one instance without problems. Many thanks

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  • Specify a base classes template parameters while instantiating a derived class?

    - by DaClown
    Hi, I have no idea if the title makes any sense but I can't find the right words to descibe my "problem" in one line. Anyway, here is my problem. There is an interface for a search: template <typename InputType, typename ResultType> class Search { public: virtual void search (InputType) = 0; virtual void getResult(ResultType&) = 0; }; and several derived classes like: template <typename InputType, typename ResultType> class XMLSearch : public Search<InputType, ResultType> { public: void search (InputType) { ... }; void getResult(ResultType&) { ... }; }; The derived classes shall be used in the source code later on. I would like to hold a simple pointer to a Search without specifying the template parameters, then assign a new XMLSearch and thereby define the template parameters of Search and XMLSearch Search *s = new XMLSearch<int, int>(); I found a way that works syntactically like what I'm trying to do, but it seems a bit odd to really use it: template <typename T> class Derived; class Base { public: template <typename T> bool GetValue(T &value) { Derived<T> *castedThis=dynamic_cast<Derived<T>* >(this); if(castedThis) return castedThis->GetValue(value); return false; } virtual void Dummy() {} }; template <typename T> class Derived : public Base { public: Derived<T>() { mValue=17; } bool GetValue(T &value) { value=mValue; return true; } T mValue; }; int main(int argc, char* argv[]) { Base *v=new Derived<int>; int i=0; if(!v->GetValue(i)) std::cout<<"Wrong type int."<<std::endl; float f=0.0; if(!v->GetValue(f)) std::cout<<"Wrong type float."<<std::endl; std::cout<<i<<std::endl<<f; char c; std::cin>>c; return 0; } Is there a better way to accomplish this?

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