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• Maintain order of messages via proxies to app servers

  - by David Turner

  Hi, I am receiving messages from a 3rd party via a http post, and it is important that the order the messages hit our infrastructure is maintained through the load balancers and proxies until it hits our application server. Quick Diagram. (proxies in place due to security requirements.) [ACE load balancer] - [2 proxies] - [Application Servers] or maybe [ACE load balancer] - [2 proxies] - [ACE load balancer] - [Application Servers] My idea was that I would setup the load balancers in active-passive mode, to force all messages to use one proxy, and then both the proxies would hit a second load balancer that would be configured in active passive to hit one application server. Whilst the above is not ideal, it does give me resilience, and once the message is in my app servers, I enter a stateless world, and load balance across both nodes of my cluster. However, I am concerned that even a single proxy could send messages out of order, perhaps if 2 messages are recived very close together, message 2 might get processed faster than message 1. Is this possible? Likely? Is there a simple open source proxy (MOD_PROXY?) that can be easily configured to just pass messages through it, and to guarantee to send the messages through in the order they are received. If so which, and finally links to how I should configure it would be great. In fact any links to articles around avoiding "out of order" messages using hardware would be gratefully received. Thanks, ps for those that are interested, the app is a java spring integration application currently on a appliation server.

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• Model relationships in ASP.NET MVC

  - by Fabiano

  Hi I recently started evaluating ASP.NET MVC. While it is really easy and quick to create Controllers and Views for Models with only primitive properties (like shown in the starter videos from the official page) I didn't find any good way to work with references to complex types. Let's say, I have these Models: public class Customer { public int Id { get; set; } public string Name { get; set; } public Address Address { get; set; } public IList<Order> Orders { get; set; } } public class Address { public int Id { get; set; } public string ..... ..... } public class Order { public int Id { get; set; } public Customer Customer { get; set; } public string OrderName { get; set; } ..... } Note that I don't have foreign keys in the models (like it's typical for LINQ to SQL, which is also used in the sample video) but an object reference. How can I handle such references in asp.net mvc? Does someone has some good tips or links to tutorials about this problem? maybe including autobinding with complex types.

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• Synchronization of Nested Data Structures between Threads in Java

  - by Dominik

  I have a cache implementation like this: class X { private final Map<String, ConcurrentMap<String, String>> structure = new HashMap...(); public String getValue(String context, String id) { // just assume for this example that there will be always an innner map final ConcurrentMap<String, String> innerStructure = structure.get(context); String value = innerStructure.get(id); if(value == null) { synchronized(structure) { // can I be sure, that this inner map will represent the last updated // state from any thread? value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } } return value; } } Is this implementation thread-safe? Can I be sure to get the last updated state from any thread inside the synchronized block? Would this behaviour change if I use a java.util.concurrent.ReentrantLock instead of a synchronized block, like this: ... if(lock.tryLock(3, SECONDS)) { try { value = innerStructure.get(id); if(value == null) { value = getValueFromSomeSlowSource(id); innerStructure.put(id, value); } } finally { lock.unlock(); } } ... I know that final instance members are synchronized between threads, but is this also true for the objects held by these members? Maybe this is a dumb question, but I don't know how to test it to be sure, that it works on every OS and every architecture.

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• Call to CFC via Ajax-POST does not work

  - by Philipp

  We have the following problem: A CFC-method that is called from AJAX suddenly redirects the request to cfcexplorer instead of executing the request. The strange thing is, that the problem only occurs when we make the ajax call via "POST" method, like this: // This will return the HTTP Status header: // Location: http://url.to:80/CFIDE/componentutils/cfcexplorer.cfc?method=getcfcinhtml&name=web.ajax&path=/web/ajax.cfc $.post( "http://url.to/ajax.cfc", {method: "test"}, function(res) { alert("ajax.cfc POST return:" + res); } ); Making the same request as "GET" request works perfectly: // This will call the method "test" of web/ajax.cfc $.get( "http://url.to/ajax.cfc", {method: "test"}, function(res) { alert("ajax.cfc GET return:" + res); } ); This is the ajax.cfc file (dummy file): <cfcomponent> <cffunction name="test" access="remote" returntype="Any" returnformat="JSON"> <cfset j = {}> <cfset j.data = "this is the data"> <cfreturn serializeJson(j)> </cffunction> </cfcomponent> What really puzzles us is that the request did work in the past (we have a lot of code all making ajax calls via POST and CF-code that expects FORM-data to be present, so we cannot simply change the method to GET) Maybe there was some setting that has changed or similar...

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• Why not systematically attach event in WPF instead of using delegate ?

  - by user310291

  For a button to handle event, we can add a delegate to the click property of the button: this.button1.Click += new System.EventHandler(this.button1_Click); But in WPF contrary to Winform, you can also attach a handler http://msdn.microsoft.com/en-us/magazine/cc785480.aspx So why not do so for the button ? Is performance better in first case maybe ? Update: I mean this Attached Events In order to enable elements to handle events that are declared in a different element, WPF supports something called attached events. Attached events are routed events that support a hookup in XAML on elements other than the type on which the event is declared. For example, if you want the Grid element to listen for a Button.Click event to bubble past, you would simply hook it up like the following: <Grid Button.Click="myButton_Click"> <Button Name="myButton" >Click Me</Button> </Grid> The resulting code in the compile-time-generated partial class now looks like this: #line 5 "..\..\Window1.xaml" ((System.Windows.Controls.Grid)(target)).AddHandler( System.Windows.Controls.Primitives.ButtonBase.ClickEvent, new System.Windows.RoutedEventHandler(this.myButton_Click));

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• Newbie question about controllers in ASP.Net MVC.

  - by Sergio Tapia

  I'm following a tutorial on creating the NerdDinner using ASP.Net MVC. However, I'm using Visual Studio 2010 Ultimate edition and there was only MVC2 to choose from. So I've following the tutorial so far, and everything is really clicking and being really well explained, until this little hitch. The guide is asking me to create new methods on a Controller file like so: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; namespace NerdDinner.Controllers { public class DinnersController : Controller { public void Index(){ Response.Write("<h1>Coming Soon: Dinners</h1>"); } public void Details(int id) { Response.Write("<h1>Details DinnerID: " + id + "</h1>"); } } } However, when I created the Controllers file, Visual Studio created an Index method already, but it looks vastly different to what the tutorial shows. Maybe this is the new way to do things using MVC2? using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; namespace NerdDinner.Controllers { public class DinnersController : Controller { // // GET: /Dinners/ public ActionResult Index() { return View(); } } } My question is, how can I reproduce the Details and Index method (they're in MVC) to the MVC2 way? Is this even relevant? Thank you!

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• Any good tutorials or resources for learning how to design a scalable and "component" based game 'fr

  - by CodeJustin.com

  In short I'm creating a 2D mmorpg and unlike my last "mmo" I started developing I want to make sure that this one will scale well and work well when I want to add new in-game features or modify existing ones. With my last attempt with an avatar chat within the first few thousand lines of code and just getting basic features added into the game I seen my code quality lowering and my ability to add new features or modify old ones was getting lower too as I added more features in. It turned into one big mess that some how ran, lol. This time I really need to buckle down and find a design that will allow me to create a game framework that will be easy to add and remove features (aka things like playing mini-games within my world or a mail system or buddy list or a new public area with interactive items). I'm thinking that maybe a component based approach MIGHT be what I'm looking for but I'm really not sure. I have read documents on mmorpg design and 2d game engine architecture but nothing really explained a way of designing a game framework that will basically let me "plug-in" new features into the main game and use the resources of the main game without changing much within my 'main game code'. Hope someone understands what I mean, any help will is appreciated.

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• A jscript variable in a Query

  - by lerac

  Maybe a very simple question. How can I put in this code <Query> <Where> <Eq> <FieldRef Name="Judge_x0020_1" /> <Value Type="Text">mr. R. Sanches</Value> </Eq> </Where> </script> </Query> A variable from jscript in the area of the code where mr. R. Sanches is written. So my jScript contains a dynamic text variable I want to replace mr. R. Sanches with. See where it says THE JAVESCRIPT VAR underneath here: <Query> <Where> <Eq> <FieldRef Name="Judge_x0020_1" /> <Value Type="Text">THE JAVASCRIPT VAR</Value> </Eq> </Where> </script> </Query>

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• Apache tomcat7 + couchdb in the same host

  - by demotics2002

  I couldn't find any guide on the internet about how to make them work together. I found some couchdb tutorials but they are mostly having the web pages hosted in couchdb's own webserver. My requirement: 1. Use tomcat 7 (or other versions) - i will be using jsp for the website. It has some features that require file upload and processing of files, file generation, and etc., that will require java. It also has admin console that will require the next item, 2. ExtJS (maybe V4) - I will be needing this in the admin console page for restful access to couchdb and other ui components (sorry but I am not considering jquery at the moment because I am already familiar with . 3. Couchdb - because the client needs a dynamic structure of data. Now my question is how to make tomcat and couchdb run on the same host (and port of course)? As much as possible I would like to avoid making my pages doing cross domain js calls. Worst case I may have to create a servlet that overrides put|get|post|delete that calls couchdb (either by using a driver or httpclient).

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• Hey Guy , I want ot streaming video by using VideView class . Can anyone tell me what format is it s

  - by eddyxd

  Hi , I am the newbie of android, but i hava seen the tutorial and implement some simple applications. The question i met is that I am tring to stream some video from my server to android, but the android VideoView class just plays the audition sololy without "image"@@!~ Here is my setting and android code : 1. android core code: mVideoView01.setVideoURI(Uri.parse("rtsp://192.168.16.1:8080/test.sdp")); mVideoView01.start(); 2. my streaming server is VLC and the command is: vlc -vvv d:\nobody.mp4 --sout=#transcode{vcodec=h264,width=320,hegiht=240}:rtp{dst=192.168.16.1,port=4444,sdp=rtsp://192.168.16.1:8080/test.sdp} ps: My ip is got from DHCP but I have checked it really can be connected(Android could play audition after all) ps2: I haved trid to stream some video from "http://www.americafree.tv/" and the playing is good!!@@ So I guess that the problem maybe is caused by streaming Video format, but I have almost tried every figument option form VLC, and it still don't workQQ. So Have anyone done the same test as me can give me some advice?? Thanks a lot!!!!! by eddy

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• Endless problems with a very simple python subprocess.Popen task

  - by Thomas

  I'd like python to send around a half-million integers in the range 0-255 each to an executable written in C++. This executable will then respond with a few thousand integers. Each on one line. This seems like it should be very simple to do with subprocess but i've had endless troubles. Right now im testing with code: // main() u32 num; std::cin >> num; u8* data = new u8[num]; for (u32 i = 0; i < num; ++i) std::cin >> data[i]; // test output / spit it back out for (u32 i = 0; i < num; ++i) std::cout << data[i] << std::endl; return 0; Building an array of strings ("data"), each like "255\n", in python and then using: output = proc.communicate("".join(data))[0] ...doesn't work (says stdin is closed, maybe too much at one time). Neither has using proc.stdin and proc.stdout worked. This should be so very simple, but I'm getting constant exceptions, and/or no output data returned to me. My Popen is currently: proc = Popen('aux/test_cpp_program', stdin=PIPE, stdout=PIPE, bufsize=1) Advise me before I pull my hair out. ;)

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• how to queue function behind ajax request

  - by user1052335

  What I'm asking is conceptual rather than why my code doesn't work. I'm trying to make a web app that displays content fetched from a database in a sequence, one at a time, and then waits for a response from the user before continuing to the next one. I'm working with javascript on the client side with the JQuery library and php on the server side. In theory, there's time while waiting for the user's input to fetch information from the server using an AJAX request and have it ready for the use by the time he clicks the button, but there's also a chance that such an AJAX request hasn't completed when he clicks the button. So I need something like pseudocode: display current information fetch next data point from the server in the background onUserInput { if ( ajax request complete) { present the information fetched in this request } else if (ajax request not complete) { wait for ajax request complete present information to user } My question is this: how does one implement this " else if (ajax request not complete) { wait for ajax request complete " part. I'm currently using JQuery for my AJAX needs. I'm somewhat new to working with AJAX, and I did search around, but I didn't find anything that seemed on point. I don't know what tools I should use for this. Some kind of queue maybe? I don't need to be spoon fed. I just need to know how this is done, using what tools or if my desired outcome would be accomplished in some other way entirely. Thanks.

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• NHibernate with Framework .NET Framework 2

  - by Daniel Dolz

  Hi. I can not make NHibernate 2.1 work in machines without framework 3.X (basically, windows 2000 SP4, although it happens with XP too). NHibernate doc do no mention this. Maybe you can help? I NEED to make NHibernate 2.1 work in Windows 2000 PCs, so you think this can be done? Thanks! PD: DataBase is SQL 2000/2005. Error is: NHibernate.MappingException: Could not compile the mapping document: Datos.NH_VEN_ComprobanteBF.hbm.xml ---> NHibernate.HibernateException: Could not instantiate dialect class NHibernate.Dialect.MsSql2000Dialect ---> System.Reflection.TargetInvocationException: Se produjo una excepción en el destino de la invocación. ---> System.TypeInitializationException: Se produjo una excepción en el inicializador de tipo de 'NHibernate.NHibernateUtil'. ---> System.TypeLoadException: No se puede cargar el tipo 'System.DateTimeOffset' del ensamblado'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. en NHibernate.Type.DateTimeOffsetType.get_ReturnedClass() en NHibernate.NHibernateUtil..cctor() --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Dialect.Dialect..ctor() en NHibernate.Dialect.MsSql2000Dialect..ctor() --- Fin del seguimiento de la pila de la excepción interna --- en System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) en System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) en System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) en System.Activator.CreateInstance(Type type, Boolean nonPublic) en NHibernate.Bytecode.ActivatorObjectsFactory.CreateInstance(Type type) en NHibernate.Dialect.Dialect.InstantiateDialect(String dialectName) --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Dialect.Dialect.InstantiateDialect(String dialectName) en NHibernate.Dialect.Dialect.GetDialect(IDictionary`2 props) en NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) --- Fin del seguimiento de la pila de la excepción interna --- en NHibernate.Cfg.Configuration.LogAndThrow(Exception exception) en NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) en NHibernate.Cfg.Configuration.ProcessMappingsQueue() and continues...

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• Looking for streaming xml pretty printer in C/C++ using expat or libxml2

  - by Mark Zeren

  I'm looking for a streaming xml pretty printer for C/C++ that's either self contained or that uses libxml2 or expat. I've searched a bit and not found one. It seems like something that would be generally useful. Am I missing an obvious tool that does this? Background: I have a library that outputs xml without whitespace all on one line. In some cases I'd like to pretty print that output. I'm looking for a BSD-ish licensed C/C++ library or sample code that will take a raw xml byte stream and pretty print it. Here's some pseudo code showing one way that I might use this functionality: void my_write(const char* buf, int len); PrettyPrinter pp(bind(&my_write)); while (...) { // ... get some more xml ... const char* buf = xmlSource.get_buf(); int len = xmlSource.get_buf_len(); int written = pp.write(buf, len); // calls my_write with pretty printed xml // ... error handling, maybe call write again, etc. ... } I'd like to avoid instantiating a DOM representation. I already have dependencies on the expat and libxml2 shared libraries, and I'd rather not add any more shared library dependencies.

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• Sortable clone helper not working

  - by Jeremy Seekamp

  Maybe I don't understand how clone works with sortable, but here is what I would like to do. When sorting an item I would like a clone of the item I am dragging remain until I stop drop the item in its new position. Here's the code: <html> <head> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.2/jquery-ui.min.js"></script> <style type="text/css"> .sort { width: 150px; } .ui-state-highlight { background-color: #000; height:2px; } </style> </head> <body> <div> <ul class="sort"> <li>Item 1</li> <li>Item 2</li> <li>Item 3</li> <li>Item 4</li> </ul> </div> <script type="text/javascript"> $(function() { $('.sort').sortable({ helper: 'clone', placeholder: 'ui-state-highlight', opacity: '.5' }) }) </script> </body> </html> Thanks in advance for the help!

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• SQL Server: A Grouping question that's annoying me

  - by user366729

  I've been working with SQL Server for the better part of a decade, and this grouping (or partitioning, or ranking...I'm not sure what the answer is!) one has me stumped. Feels like it should be an easy one, too. I'll generalize my problem: Let's say I have 3 employees (don't worry about them quitting or anything...there's always 3), and I keep up with how I distribute their salaries on a monthly basis. Month Employee PercentOfTotal -------------------------------- 1 Alice 25% 1 Barbara 65% 1 Claire 10% 2 Alice 25% 2 Barbara 50% 2 Claire 25% 3 Alice 25% 3 Barbara 65% 3 Claire 10% As you can see, I've paid them the same percent in Months 1 and 3, but in Month 2, I've given Alice the same 25%, but Barbara got 50% and Claire got 25%. What I want to know is all the distinct distributions I've ever given. In this case there would be two -- one for months 1 and 3, and one for month 2. I'd expect the results to look something like this (NOTE: the ID, or sequencer, or whatever, doesn't matter) ID Employee PercentOfTotal -------------------------------- X Alice 25% X Barbara 65% X Claire 10% Y Alice 25% Y Barbara 50% Y Claire 25% Seems easy, right? I'm stumped! Anyone have an elegant solution? I just put together this solution while writing this question, which seems to work, but I'm wondering if there's a better way. Or maybe a different way from which I'll learn something. WITH temp_ids (Month) AS ( SELECT DISTINCT MIN(Month) FROM employees_paid GROUP BY PercentOfTotal ) SELECT EMP.Month, EMP.Employee, EMP.PercentOfTotal FROM employees_paid EMP JOIN temp_ids IDS ON EMP.Month = IDS.Month GROUP BY EMP.Month, EMP.Employee, EMP.PercentOfTotal Thanks y'all! -Ricky

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• Exam Questions that use .Demand or .LinkDemand COULD NOT BE ANY MORE CONFUSING OR AMBIGIOUS ????

  - by IbrarMumtaz

  I am 110% sure this is WRONG !!!! Q.12) You develop a library, and want to ensure that the functions in the library cannot be either directly or indirectly invoked by applications that are not running on the local intranet. What attribute would you add to each method? A. [UrlIdentityPermission(SecurityAction.RequestRefuse, Url="http://myintranet")] B. [UrlIdentityPermission(SecurityAction.LinkDemand, Url="http://myintranet")] (correct answer) C. [UrlIdentityPermission(SecurityAction.Demand, Url="http://myintranet")] D. [UrlIdentityPermission(SecurityAction.Assert, Url="http://myintranet")] Explanation Link-Demand should be used as it ensures that all callers in the call stack have the necessary permission. In this case it ensures that all callers in the call stack are on the local intranet. There is an indentical question on Transencer so I already had a clue what was goin but Transcender was much more informative that this drivel as it mentioned class level and not assembly level. It also mentioned that some callers maybe coming externally from the company intranet via authroised and authenticated credentials. With information is easy to see why .Demand on would be wong option to go for? So Transcender was right .... so I thgt fine, that makes sense. With think information still fresh in my brain I had a good idea was was going on in the question. To my surprise .Demand was wrong agin !!!! WHAT? I am really starting to hate this setting now? I cannot be any more p*ssed right now!!! :@ Thanks For Reading, Ibrar

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• Create an anonymous type object from an arbitrary text file

  - by Robert Harvey

  I need a sensible way to draw arbitrary text files into a C# program, and produce an arbitrary anonymous type object, or perhaps a composite dictionary of some sort. I have a representative text file that looks like this: adapter 1: LPe11002 Factory IEEE: 10000000 C97A83FC Non-Volatile WWPN: 10000000 C93D6A8A , WWNN: 20000000 C93D6A8A adapter 2: LPe11002 Factory IEEE: 10000000 C97A83FD Non-Volatile WWPN: 10000000 C93D6A8B , WWNN: 20000000 C93D6A8B Is there a way to get this information into an anonymous type object or some similar structure? The final anonymous type might look something like this, if it were composed in C# by hand: new { adapter1 = new { FactoryIEEE = "10000000 C97A83FC", Non-VolatileWWPN = "10000000 C93D6A8A", WWNN = "20000000 C93D6A8A" } adapter2 = new { FactoryIEEE = "10000000 C97A83FD", Non-VolatileWWPN = "10000000 C93D6A8B", WWNN = "20000000 C93D6A8B" } } Note that, as the text file's content is arbitrary (i.e. the keys could be anything), a specialized solution (e.g. that looks for names like "FactoryIEEE") won't work. However, the structure of the file will always be the same (i.e. indentation for groups, colons and commas as delimiters, etc). Or maybe I'm going about this the wrong way, and you have a better idea?

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• AVAudioPlayer working in Simulator, but not on device

  - by cannyboy

  My mp3 playing code is: NSError *error; soundObject = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:audioPathString] error:&error]; if (soundObject == nil) NSLog(@"%@", [error description]); soundObject.delegate = self; soundObject.numberOfLoops = 0; soundObject.volume = 1.0; NSLog(@"about to play"); [soundObject prepareToPlay]; [soundObject play]; NSLog(@"[soundObject play];"); The mp3 used to play fine, and it still does on the simulator. But not on the device. I've recently added some sound recording code (not mine) to the software. It uses AudioQueue stuff which is slightly beyond me. Does that conflict with AVAudioPlayer? Or what could be the problem? I've noticed that as soon as the audiorecording code starts working, I can't adjust the volume on the device anymore, so maybe it blocks the audio playback?. EDIT The solution seems to be to put this in my code. I put it in applicationDidFinishLaunching: [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayAndRecord error: nil]; UInt32 audioRouteOverride = kAudioSessionOverrideAudioRoute_Speaker; AudioSessionSetProperty (kAudioSessionProperty_OverrideAudioRoute,sizeof (audioRouteOverride),&audioRouteOverride); The first line allows both play and record, whilst the other lines apparently reroute things to make the volume louder. All audio code is voodoo to me.

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• Sorting, Filtering and Paging in ASP.NET MVC

  - by ali62b

  What is the best approach to implement these features and which part of project would involved? I see some example of JavaScript grids, but I'm talking about a general approach which best fits the MVC architecture. I've considered configuring routes and models to implement these features but I don't have a clear idea that if this is the right approach to implementing such features. On the one hand, I think if we put logic in routes (item/page/sort/), we would have benefits like bookmarking and avoiding JavaScript. On the other hand if we use JavaScript grids, we can have behavior like the old school grid views in ASP.NET web forms. I find that using HTML helpers may be useful for paging, but have no idea if they are good for sorting or not. I've looked at jQuery, tableSorter and quick search plug-ins, but they work just on the currently-fetched data and won't help in real sorting and filtering that may need to touch the database. I have some thoughts on using these tools side by side with AJAX to get something which works, but I have no idea if there are similar efforts done yet anywhere. Another approach I looked at was using Dynamic Data on web forms, but I didn't find any suggestions out there as to whether or not it is a good idea to integrate MVC and DD. I know implementing filtering and sorting for an individual case is simple (although it has some issues like using Dynamic LINQ, which is not yet a standard approach), but creating a sorting or filtering tool which works in all cases is the idea I'm looking for. (Maybe this is because I want have something in hand when web form developers are wondering why I'm writing same code each time I want to implement a sort scenario for different Entities).

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• Objective-C Simple Inheritance and OO Principles

  - by bleeckerj

  I have a subclass SubClass that inherits from baseclass BaseClass. BaseClass has an initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.goodStuff = [[NSMutableArray alloc]init]; } SubClass does its initializer, like so: -(id)init { self = [super init]; if(self) { [self commonInit]; } return self; } -(void)commonInit { self.extraGoodStuff = [[NSMutableArray alloc]init]; } Now, I've *never taken a proper Objective-C course, but I'm a programmer more from the Electrical Engineering side, so I make do. I've developed server-side applications mostly in Java though, so I may be seeing the OO world through Java principles. When SubClass is initialized, it calls the BaseClass init and my expectation would be — because inheritance to me implies that characteristics of a BaseClass pass through to SubClass — that the commonInit method in BaseClass would be called during BaseClass init. It is not. I can *sorta understand maybe-possibly-stretch-my-imagination why it wouldn't be. But, then — why wouldn't it be based on the principles of OOP? What does "self" represent if not the instance of the class of the running code? Okay, so — I'm not going to argue that what a well-developed edition of Objective-C is doing is wrong. So, then — what is the pattern I should be using in this case? I want SubClass to have two main bits — the goodStuff that BaseClass has as well as the extraGoodStuff that it deserves as well. Clearly, I've been using the wrong pattern in this type of situation. Am I meant to expose commonInit (which makes me wonder about encapsulation principles — why expose something that, in the Java world at least, would be considered "protected" and something that should only ever be called once for each instance)? I've run into a similar problem in the recent past and tried to muddle through it, but now — I'm really wondering if I've got my principles and concepts all straight in my head. Little help, please.

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• Can you force a crash if a write occurs to a given memory location with finer than page granularity?

  - by Joseph Garvin

  I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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• Get the parent id..

  - by tixrus

  I have a bunch of elements like the following: <div class="droppableP" id="s-NSW" style="width:78px; height:63px; position: absolute; top: 223px; left: 532px;"> </div> They all have class droppableP but different id's obviously and I would like to factor the code in this script I am hacking on. The original script just has a specific selector for each of one of these divs, but the code is all alike except for the id it does things to, which is either the id of the parent or another div with a name that's related to it. Here is the original code specifically for this div: $("#s-NSW > .sensible").droppable( { accept : "#i-NSW", tolerance : 'intersect', activeClass : 'droppable-active', hoverClass : 'droppable-hover', drop : function() { $('#s-NSW').addClass('s-NSW'); $('#s-NSW').addClass('encastrada'); //can't move any more.. $('#i-NSW').remove(); $('#s-NSW').animate( { opacity: 0.25 },200, 'linear'); checkWin(); } }); Here is how I would like to factor so the same code can do all of them and I will eventually do chaining as well and maybe get rid of the inline styles but here is my first go: $(".droppableP > .sensible").droppable( { accept : "#i" + $(this).parent().attr('id').substring(2), tolerance : 'intersect', activeClass : 'droppable-active', hoverClass : 'droppable-hover', drop : function() { $(this).parent().addClass($(this).parent().attr('id')); $(this).parent().addClass('encastrada'); $("#i" + ($this).parent().attr('id').substring(2)).remove(); $(this).parent().animate( { opacity: 0.25 },200, 'linear'); checkWin(); } }); The error I get is $(this).parent().attr("id") is undefined Many thanks. I have browsed related questions the one I understand that's closest to mine, turns out they didn't need parent function at all. I'm kind of a noob so please don't yell at me too hard if this is a stupid question.

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• Better viewing of postfix mail queue files than postcat?

  - by Geekman

  So I got a call early this morning about a client needing to see what email they have waiting to be delivered sitting in our secondary mail server. Their link for the main server had (still is) been down for two days and they needed to see their email. So I wrote up a quick perl script to use mailq in combination with postcat to dump each email for their address into separate files, tar'd it up and sent it off. Horrible code, I know, but it was urgent. My solution works OK in that it at least gives a raw view, but I thought tonight it would be nice if I had a solution where I could provide their email attachments and maybe remove some "garbage" header text as well. Most of the important emails seem to have a PDF or similar attached. I've been looking around but the only method of viewing queue files I can see is the postcat command, and I really don't want to write my own parser - so I was wondering if any of you have already done so, or know of a better command to use? Here's the code for my current solution: #!/usr/bin/perl $qCmd="mailq | grep -B 2 \"someemailaddress@isp\" | cut -d \" \" -f 1"; @data = split(/\n/, `$qCmd`); $i = 0; foreach $line (@data) { $i++; $remainder = $i % 2; if ($remainder == 0) { next; } if ($line =~ /\(/ || $line =~ /\n/ || $line eq "") { next; } print "Processing: " . $line . "\n"; `postcat -q $line > $line.email.txt`; $subject=`cat $line.email.txt | grep "Subject:"`; #print "SUB" . $subject; #`cat $line.email.txt > \"$subject.$line.email.txt\"`; } Any advice appreciated.

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• qt on Win CE 5.0 crash

  - by Michael

  Good day all, It's the first time I am using Qt on Windows CE and I ran into an issue. Maybe someone can help me with it. I will describe my set up. I am using XP with Visual Studio 2005 an Qt Add-in version 1.1.2. I downloaded Qt source for Windows CE and followed the instructions on these (http://doc.trolltech.com/4.4/install-wince.html) instructions to build the library for CE. I then used the Visual Studio to create a minimal Qt Windows CE Application. The program runs fine in the CE emulator, but once I try to deploy it on the device it crashes with the following message: Load module: qt_ce_3.exe Load module: QtGui4.dll Load module: msvcr80.dll Load module: QtCore4.dll Load module: CEShell.DLL Load module: OLEAUT32.dll Load module: commctrl.dll.0409.MUI Load module: commctrl.dll Load module: aygshell.dll Load module: WS2.dll Load module: WINSOCK.dll Load module: coredll.dll.0409.MUI Load module: ossvcs.dll Load module: ole32.dll Load module: coredll.dll Load module: MMTimer.dll Data Abort: Thread=8fb09a40 Proc=8c4ecea0 'qt_ce_3.exe' AKY=00040001 PC=012a80b0(qtcore4.dll+0x000680b0) RA=012a8168(qtcore4.dll+0x00068168) BVA=676e4574 FSR=000000f5 Unhandled exception at 0x012a80b0 in qt_ce_3.exe: 0xC0000005: Access violation reading location 0x676e4574. I tried it on two devices from different manufacturers, and the result is the same. Debug version worked on one of them, ran out of memory on the other. Does anyone have any idea what this could be? Thanks in advance, Michael

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