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  • Suggestion for setting web application parameters

    - by user40730
    I'm creating a web application on GWT. I'm using MVP pattern with activities and places. I have a xml config file containing some parameters to be used by the application. Content of this xml file is sent to the client using HttpRequest; I'm using a singleton class to hold the information from the xml file. Right now, the application is getting the data when the user starts the application in the home page, that is working well. Now, since I'm using activities and places, a user can bookmark a page and starts the application in any other page (Place). And here comes the problem: Since I'm using some of the information from the xml file to set some ui widgets, I have to check if the xml config file was read and the application already has the parameters (I do this by checking the singleton class). But the xml file is read by using an HttpRequest, so I got errors 'cause the application needs some parameters to initialize some ui widgets, but these parameters aren't ready on time. I was thinking on using an synchronous request to fix the problem, but it seems complicated and not recommendable to do that. So, I'd like to hear some other suggestions. Thanks.

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  • Design help with parallel process

    - by brazc0re
    I am re-factoring some code and an having an issue with retrieving data from two parallel processes. I have an application that sends packets back and forth via different mediums (ex: RS232, TCP/IP, etc). The jist if of this question is that there are two parallel processes going on. I hope the picture below displays what is going on better than I can word it: SetupRS232() class creates a new instance of the SerialPort by: SerialPort serialPort = new SerialPort(); My question is, what is the best way that the Communicator() class, which sends out the packet via the respective medium, get access to the SerialPort object from the SetupRS232 class? I can do it with a Singleton but have heard that they are generally not the best design to go by. I am trying to follow SRP but I do feel like I am doing something wrong here. Communicator() will need to go out of it's way to get access to SetupRS232() to get access to the SerialPort class. I actually haven't found a way to even get access to it. Would designing each medium class, for example, SetupRS232(), SetupTCPIP, as a singleton be the best way to approach this problem?

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  • Informing GUI objects about screen size - Designing

    - by Mosquito
    I have a problem with designing classes for my game which I create. In my app, there is: class CGame which contains all the information about game itself, e.g. screen width, screen height, etc. In the main() function I create a pointer to CGame instance. class CGUIObject which includes fields specifying it's position and draw() method, which should know how to draw an object according to screen size. class CGUIManager which is a singleton and it includes a list of CGUIObject's. For each object in a list it just calls draw() method. For clarity's sake, I'll put some simple code: class CGame { int screenWidth; int screenHeight; }; class CGUIObject { CPoint position; void draw(); // this one needs to know what is a screen's width and height }; class CGUIManager // it's a singleton { vector<CGUIObject*> guiObjects; void drawObjects(); }; And the main.cpp: CGame* g; int main() { g = new CGame(); while(1) { CGUIManager::Instance().drawObjects(); } return 0; } Now the problem is, that each CGUIObject needs to know the screen size which is held by CGame, but I find it very dumb to include pointer to CGame instance in every object. Could anyone, please, tell me what would be the best approach to achieve this?

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  • Should static parameters in an API be part of each method?

    - by jschoen
    I am currently creating a library that is a wrapper for an online API. The obvious end goal is to make it as easy for others to use as possible. As such I am trying to determine the best approach when it comes to common parameters for the API. In my current situation there are 3 (consumer key, consumer secret, and and authorization token). They are essentially needed in every API call. My question is should I make these 3 parameters required for each method or is there a better way. I see my current options as being: Place the parameters in each method call public ApiObject callMethod(String consumerKey, String consumerSecret, String token, ...) This one seems reasonable, but seems awfully repetitive to me. Create a singleton class that the user must initialize before calling any api methods. This seems wrong, and would essentially limit them to accessing one account at a time via the API (which may be reasonable, I dunno). Make them place them in a properties file in their project. That way I can load the properties that way and store them. This seems similar to the singleton to me, but they would not have to explicitly call something to initialize these values. Is there another option I am not seeing, or a more common practice in this situation that I should be following?

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  • Contructor parameters for dependent classes with Unity Framework

    - by Onisemus
    I just started using the Unity Application Block to try to decouple my classes and make it easier for unit testing. I ran into a problem though that I'm not sure how to get around. Looked through the documentation and did some Googling but I'm coming up dry. Here's the situation: I have a facade-type class which is a chat bot. It is a singleton class which handles all sort of secondary classes and provides a central place to launch and configure the bot. I also have a class called AccessManager which, well, manages access to bot commands and resources. Boiled down to the essence, I have the classes set up like so. public class Bot { public string Owner { get; private set; } public string WorkingDirectory { get; private set; } private IAccessManager AccessManager; private Bot() { // do some setup // LoadConfig sets the Owner & WorkingDirectory variables LoadConfig(); // init the access mmanager AccessManager = new MyAccessManager(this); } public static Bot Instance() { // singleton code } ... } And the AccessManager class: public class MyAccessManager : IAccessManager { private Bot botReference; public MyAccesManager(Bot botReference) { this.botReference = botReference; SetOwnerAccess(botReference.Owner); } private void LoadConfig() { string configPath = Path.Combine( botReference.WorkingDirectory, "access.config"); // do stuff to read from config file } ... } I would like to change this design to use the Unity Application Block. I'd like to use Unity to generate the Bot singleton and to load the AccessManager interface in some sort of bootstrapping method that runs before anything else does. public static void BootStrapSystem() { IUnityContainer container = new UnityContainer(); // create new bot instance Bot newBot = Bot.Instance(); // register bot instance container.RegisterInstance<Bot>(newBot); // register access manager container.RegisterType<IAccessManager,MyAccessManager>(newBot); } And when I want to get a reference to the Access Manager inside the Bot constructor I can just do: IAcessManager accessManager = container.Resolve<IAccessManager>(); And elsewhere in the system to get a reference to the Bot singleton: // do this Bot botInstance = container.Resolve<Bot>(); // instead of this Bot botInstance = Bot.Instance(); The problem is the method BootStrapSystem() is going to blow up. When I create a bot instance it's going to try to resolve IAccessManager but won't be able to because I haven't registered the types yet (that's the next line). But I can't move the registration in front of the Bot creation because as part of the registration I need to pass the Bot as a parameter! Circular dependencies!! Gah!!! This indicates to me I have a flaw in the way I have this structured. But how do I fix it? Help!!

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  • Matlab matrix replacement assignment gives error

    - by Gulcan
    Hello, when i tried to update some part of a matrix, i got the following error message: ??? Assignment has fewer non-singleton rhs dimensions than non-singleton subscripts My code tries to update some values of a matrix that represent a binary image. My code is as follows: outImage(3:5,2:4,1) = max(imBinary(3:5,2:4,1)); When I delete last parameter (1), this time I get the same error. I guess there is a mismatch between dimensions but I could not get it. outImage is a new object that is created at that time (I tried to create it before, but nothing changed). What may be wrong? Thanks in advance, Gulcan

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  • MATLAB matrix replacement assignment gives error

    - by Gulcan
    I tried to update some part of a matrix, I got the following error message: ??? Assignment has fewer non-singleton rhs dimensions than non-singleton subscripts My code tries to update some values of a matrix that represent a binary image. My code is as follows: outImage(3:5,2:4,1) = max(imBinary(3:5,2:4,1)); When I delete last parameter (1), this time I get the same error. I guess there is a mismatch between dimensions but I could not get it. outImage is a new object that is created at that time (I tried to create it before, but nothing changed). What may be wrong?

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  • double checked locking - objective c

    - by bandejapaisa
    I realised double checked locking is flawed in java due to the memory model, but that is usually associated with the singleton pattern and optimizing the creation of the singleton. What about under this case in objective-c: I have a boolean flag to determine if my application is streaming data or not. I have 3 methods, startStreaming, stopStreaming, streamingDataReceived and i protect them from multiple threads using: - (void) streamingDataReceived:(StreamingData *)streamingData { if (self.isStreaming) { @synchronized(self) { if (self.isStreaming) { - (void) stopStreaming { if (self.isStreaming) { @synchronized(self) { if (self.isStreaming) { - (void) startStreaming:(NSArray *)watchlistInstrumentData { if (!self.isStreaming) { @synchronized(self) { if (!self.isStreaming) { Is this double check uneccessary? Does the double check have similar problems in objective-c as in java? What are the alternatives to this pattern (anti-pattern). Thanks

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  • Spring: Using "Lookup method injection" for my ThreadFactory looks not scalable.

    - by Michael Bavin
    Hi, We're building a ThreadFactory so everytime a singleton controller needs a new thread, i get a new instance everytime. Looking at Lookup method injection looks good but what if we have multiple threads. like: public abstract class ThreadManager { public abstract Thread createThreadDoA(); public abstract Thread createThreadDoB(); } and config: <bean id="threadManager" class="bla.ThreadManager" singleton="true"> <lookup-method name="createThreadA" bean="threadA" /> <lookup-method name="createThreadB" bean="threadB"/> </bean> <bean id="threadA" class="bla.ThreadA"> <bean id="threadB" class="bla.ThreadB"> and usage: threadManager.createThreadA(); I don't want to create an abstract "create" method for every new threadclass. Is it possible to make this generich like: threadManager.createThread(ThreadA.class); Thank you

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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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  • Useful Eclipse Java Code Templates

    - by Jon
    You can create various Java code templates in Eclipse via the Window->Preferences->Java -> Editor -> Templates e.g. sysout is expanded to: System.out.println(${word_selection}${});${cursor} You can activate this by typing sysout followed by CTRL+SPACE What useful Java code templates do you currently use? Include the name and description of it and why it's awesome. There's an open bounty on this for an original/novel use of a template rather than a built-in existing feature. Create Log4J logger Get swt color from display Syncexec - Eclipse Framework Singleton Pattern/Enum Singleton Generation Readfile Const Traceout Format String Comment Code Review String format Try Finally Lock Message Format i18n and log Equalsbuilder Hashcodebuilder Spring Object Injection Create FileOutputStream

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  • linq to sql datacontext for a web application

    - by rap-uvic
    Hello, I'm trying to use linq to sql for my project (very short deadline), and I'm kind of in a bind. I don't know the best way to have a data context handy per request thread. I want something like a singleton class from which all my repository classes can access the current data context. However, singleton class is static and is not thread-safe and therefore not suitable for web apps. I want something that would create a data context at the beginning of the request and dispose of it along with the request. Can anyone please share their solution to this problem? I've been searching for a solution and I've found a good post from Rick Strahl : http://www.west-wind.com/weblog/posts/246222.aspx but I don't completely understand his thread-safe or business object approach. If somebody has a simplified version of his thread-safe approach, i'd love to take a look.

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  • Will pool the connection help threading in sqlite (and how)?

    - by mamcx
    I currently use a singleton to acces my database (see related question) but now when try to add some background processing everything fall apart. I read the sqlite docs and found that sqlite could work thread-safe, but each thread must have their own db connection. I try using egodatabase that promise a sqlite wrapper with thread safety but is very buggy, so I return to my old FMDB library I start to see how use it in multi-thread way. Because I have all code with the idea of singleton, change everything will be expensive (and a lot of open/close connections could become slow), so I wonder if, as the sqlite docs hint, build a pooling for each connection will help. If is the case, how make it? How know wich connection get from the pool (because 2 threads can't share the connection)? I wonder if somebody already use sqlite in multu-threading with NSOperation or similar stuff, my searching only return "yeah, its possible" but let the details to my imagination...

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  • A question about making a C# class persistent during a file load

    - by Adam
    Apologies for the indescriptive title, however it's the best I could think of for the moment. Basically, I've written a singleton class that loads files into a database. These files are typically large, and take hours to process. What I am looking for is to make a method where I can have this class running, and be able to call methods from within it, even if it's calling class is shut down. The singleton class is simple. It starts a thread that loads the file into the database, while having methods to report on the current status. In a nutshell it's al little like this: public sealed class BulkFileLoader { static BulkFileLoader instance = null; int currentCount = 0; BulkFileLoader() public static BulkFileLoader Instance { // Instanciate the instance class if necessary, and return it } public void Go() { // kick of 'ProcessFile' thread } public void GetCurrentCount() { return currentCount; } private void ProcessFile() { while (more rows in the import file) { // insert the row into the database currentCount++; } } } The idea is that you can get an instance of BulkFileLoader to execute, which will process a file to load, while at any time you can get realtime updates on the number of rows its done so far using the GetCurrentCount() method. This works fine, except the calling class needs to stay open the whole time for the processing to continue. As soon as I stop the calling class, the BulkFileLoader instance is removed, and it stops processing the file. What I am after is a solution where it will continue to run independently, regardless of what happens to the calling class. I then tried another approach. I created a simple console application that kicks off the BulkFileLoader, and then wrapped it around as a process. This fixes one problem, since now when I kick off the process, the file will continue to load even if I close the class that called the process. However, now the problem I have is that cannot get updates on the current count, since if I try and get the instance of BulkFileLoader (which, as mentioned before is a singleton), it creates a new instance, rather than returning the instance that is currently in the executing process. It would appear that singletons don't extend into the scope of other processes running on the machine. In the end, I want to be able to kick off the BulkFileLoader, and at any time be able to find out how many rows it's processed. However, that is even if I close the application I used to start it. Can anyone see a solution to my problem?

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  • iphone threading speed up startup of app

    - by BahaiResearch.com
    I have an app that must get data from the Sqlite database in order to display the first element to the User. I have created a domain object which wraps the DB access and is a thread safe singleton. Is this following strategy optimal to ensure the fastest load given the iPhone's file access and memory management capabilities in threaded apps: 1) In the AppDelegate's FinishedLaunching event the very first thing I do is create the domain singleton within a new thread. This will cause the domain object to go to Sqlite and get the data it needs without locking the UI thread. 2) I then call the standard Window methods to add the View and MakeKeyAndVisible etc. Is there an earlier stage in the AppDelegate where I should fire off the thread that creates the Domain Object and accesses Sqlite?

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  • Stored Connection Strings per user

    - by pehaada
    In the past I've used a Singleton Pattern to load the connection string when the application starts via the global.asa file. I have a project now where each user has a unique connection string to the database. I would like to load this connection string once. The issue is that the singleton pattern will not work for me since each user has there own connection string. Basically the connection string is created dynamically. I do not want to store it is session. If anyway has a clever way of doing this in .NET let me know ?

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  • Singletons vs. Application Context in Android?

    - by mschonaker
    Recalling this post enumerating several problems of using singletons and having seen several examples of Android applications using singleton pattern, I wonder if it's a good idea to use Singletons instead of single instances shared through global application state (subclassing android.os.Application and obtaining it through context.getApplication()). What advantages/drawbacks would have both mechanisms? To be honest, I expect the same answer in this post http://stackoverflow.com/questions/2709071/singleton-pattern-with-web-application-not-a-good-idea but applied to Android. Am I correct? What's different in DalvikVM otherwise? EDIT: I would like to have opinions on several aspects involved: Synchronization Reusability Testing Thanks in advance.

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  • C++ Add this pointer to a container by calling it in base class constructor

    - by vivekeviv
    class Base { public: Base (int a, int b); private: int a,b; }; class Derived1 { public: Derived1():base(1,2){} }; similarly Derived2, Derived 3 which doesnt contain any data members on its own Now i need to contain these derived objects in a singleton, so i was thinking to call this in base constructor like Base::Base(int a, int b) { CBaseMgr::GetInstance()->AddtoVector(this); } so now if i construct Derived d1, d2, d3 etc. will the Singleton's container contain all derived objects? My doubt is can i do this adding of objects to container in base ctor or should i do in derived ctor.?

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  • Application wide messaging... without singletons?

    - by StormianRootSolver
    So, I want to go for a more Singleton - less design in the future. However, there seem to be a lot of tasks in an application that can't be done in meaningful way without singletons. I call them "application wide services", but they also fall into the same category as the cross cutting concerns, which I usually fix via AOP. Lets take an example: I want an application wide message queue that dispatches messages to components, every component can subscribe and publish there, it's a very nice multicast thing. The message queue and dispatching system are usually a (rather short) singleton class, which is very easy to implement in, say, C#. You can even use double dispatching and utilize message type metadata and the like, it's all so easy to do, it's almost trivial. However, having singletons is not really "object oriented design" (it introduces global variables) and it makes testing harder. Do you have any ideas? I'm asking this question because I'm willing to learn more about this topic, a LOT more. :-)

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  • StructureMap: How can i unit test the registry class?

    - by Marius
    I have a registry class like this: public class StructureMapRegistry : Registry { public StructureMapRegistry() { For<IDateTimeProvider>().Singleton().Use<DateTimeProviderReturningDateTimeNow>(); } I want to test that the configuration is according to my intent, so i start writing a test: public class WhenConfiguringIOCContainer : Scenario { private TfsTimeMachine.Domain.StructureMapRegistry registry; private Container container; protected override void Given() { registry = new TfsTimeMachine.Domain.StructureMapRegistry(); container = new Container(); } protected override void When() { container.Configure(i => i.AddRegistry(registry)); } [Then] public void DateTimeProviderIsRegisteredAsSingleton() { // I want to say "verify that the container contains the expected type and that the expected type // is registered as a singleton } } How can verify that the registry is accoring to my expectations? Note: I introduced the container because I didn't see any sort of verification methods available on the Registry class. Idealy, I want to test on the registry class directly.

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  • A question about making a C# class persistant during a file load

    - by Adam
    Apologies for the indescriptive title, however it's the best I could think of for the moment. Basically, I've written a singleton class that loads files into a database. These files are typically large, and take hours to process. What I am looking for is to make a method where I can have this class running, and be able to call methods from within it, even if it's calling class is shut down. The singleton class is simple. It starts a thread that loads the file into the database, while having methods to report on the current status. In a nutshell it's al little like this: public sealed class BulkFileLoader { static BulkFileLoader instance = null; int currentCount = 0; BulkFileLoader() public static BulkFileLoader Instance { // Instanciate the instance class if necessary, and return it } public void Go() { // kick of 'ProcessFile' thread } public void GetCurrentCount() { return currentCount; } private void ProcessFile() { while (more rows in the import file) { // insert the row into the database currentCount++; } } } The idea is that you can get an instance of BulkFileLoader to execute, which will process a file to load, while at any time you can get realtime updates on the number of rows its done so far using the GetCurrentCount() method. This works fine, except the calling class needs to stay open the whole time for the processing to continue. As soon as I stop the calling class, the BulkFileLoader instance is removed, and it stops processing the file. What I am after is a solution where it will continue to run independently, regardless of what happens to the calling class. I then tried another approach. I created a simple console application that kicks off the BulkFileLoader, and then wrapped it around as a process. This fixes one problem, since now when I kick off the process, the file will continue to load even if I close the class that called the process. However, now the problem I have is that cannot get updates on the current count, since if I try and get the instance of BulkFileLoader (which, as mentioned before is a singleton), it creates a new instance, rather than returning the instance that is currently in the executing process. It would appear that singletons don't extend into the scope of other processes running on the machine. In the end, I want to be able to kick off the BulkFileLoader, and at any time be able to find out how many rows it's processed. However, that is even if I close the application I used to start it. Can anyone see a solution to my problem?

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  • How to handle request/response propagation up and down a widget hierarchy in a GUI app?

    - by fig-gnuton
    Given a GUI application where widgets can be composed of other widgets: If the user triggers an event resulting in a lower level widget needing data from a model, what's the cleanest way to be able to send that request to a controller (or the datastore itself)? And subsequently get the response back to that widget? Presumably one wouldn't want the controller or datastore to be a singleton directly available to all levels of widgets, or is this an acceptable use of singleton? Or should a top level controller be injected as a dependency through a widget hierarchy, as far down as the lowest level widget that might need that controller? Or a different approach entirely?

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  • Talend vs. SSIS: A Simple Performance Comparison

    With all of the ETL tools in the marketplace, which one is best? Jeff Singleton brings us simple performance comparison pitting SSIS against open source powerhouse Talend. Optimize SQL Server performance“With SQL Monitor, we can be proactive in our optimization process, instead of waiting until a customer reports a problem,” John Trumbul, Sr. Software Engineer. Optimize your servers with a free trial.

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  • GoF Design Patterns - which ones do you actually use?

    - by CraigS
    I'm trying to educate my colleagues in the area of design patterns. Some of the original Gang of Four patterns are a little esoteric, so I'm wondering if there is a sub-group of "essential" patterns that all programmers should know. As I look through the list, I think I've probably used - Abstract Factory Factory Method Singleton Bridge Facade Command Which ones do you actually use in practice, and what do you use them for? Link for those wanting a list of patterns

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  • Custom errors won't turn off (2 replies)

    ..NET Framework 3.5 Visual Studio 2008 C# I implemented my own transport channel. It works to a point: the client is capable of invoking a method on a server singleton. When the method completes successfully it exits and back on the client I receive: System.Runtime.Remoting.RemotingException was unhandled Message &quot;Server encountered an internal error. For more information, turn off customErrors in...

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