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  • Singleton with eager initialization

    - by jesper
    I have class X that takes much time to initialize itself. I want to make that class singleton and force its creation when rails application starts. I've made the singleton: class X @@instance = nil def self.instance if @@instance.nil? @@instance = X.new puts 'CREATING' end return @@instance end private_class_method :new end The problem is that every time I use this class I see 'CREATING' in logs. I've tried to put creation of class in initializers directory but it doesn't work either.

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  • Example of Singleton pattern

    - by Supereme
    Hi, Can anybody tell me a good example of Singleton pattern? Also I've one doubt to ask, Is the following scenario is that of singleton pattern: When we have many printers connected in LAN but only one printer queue?

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  • Singleton & Multithreading in Java

    - by vivek jagtap
    What is the preferred way to work with Singleton class in multithreaded environment? Suppose if I have 3 thread, and all they try to access getInstance() method of singleton class at the same time - What would happen if no synchronization is maintained? Is it good practice to use synchronized getInstance() method or use synchronized block inside getInstance(). Please advise if there is any other way out.

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  • Free Windows Application Blocker/Monitor

    - by Click Ok
    I want a free application monitor that when detects certain keywords on window title by example, it closes the application (or prevents that it opens/install). Nice extra will be if the program log the application activity too and internet sites accessed by any browser. Thank you very much! PS: I'm using Windows 7 Ultimate.

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  • [PHP] Making a good singleton registry class structure which hold your objects

    - by Saif Bechan
    I am working on a web application in PHP. I have a singleton class called registry. This class will hold all the objects i need throughout my application, such as loader classes, template classes, database, classes, etc. When an object of the registry class is created I send it an array with the classes it need to load: // Create the registry $registry = registry::singleton(); // Store those core objects $registry->storeObjects(Array('session','db','page','template','errors')); In this example I only put some of the classes, to get the basic idea. Now I have some classes in the registry that use each other. For example the 'errors' object uses the 'page' object. Now I was wondering if it is a good practice to make an instance of the registry object in the errors object. Like this; class errors{ private $registry; public function __construct(){ $this->registry = registry::singleton(); } } So there is an instance of the registry object, inside an object of the registry object. This does not sound like a good idea to me. Anyone have a suggestion how to model such a thing?

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  • Call from a singleton class to a function which in turn calls that class's method

    - by dare2be
    Hello, I am still looking for a way to phrase it properly (I'm not a native speaker...). So I have this class SQL which implements the singleton pattern (for obvious reasons) and I also have this function, checkUsr(), which queries the database using one of SQL's methods. Everything works fine as long as I don't call checkUsr() from within the SQL class. When I do so, the scripts just exits and a blank page is displayed - no errors are returned, no exception is thrown... What's happening? And how do I work around this problem? EDIT: class SQL { public static function singleton() { static $instance; if(!isset($instance)) $instance = new SQL; return $instance; } public function tryLoginAuthor( $login, $sha1 ) { (...) } } function checkUsr() { if (!isset($_SESSION['login']) || !isset($_SESSION['sha1'])) throw new Exception('Not logged in', 1); $SQL = SQL::singleton(); $res = $SQL->tryLoginAuthor($_SESSION['login'], $_SESSION['sha1']); if (!isset($res[0])) throw new Exception('Not logged in', 1); }

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  • What is the best way to create a Singleton Webservice in PHP?

    - by ChronoFish
    Hello, We have a need to access a DB that only allows one connection at a time. This screams "singleton" to me. The catch of course is that the singleton connection will be exposed (either directly or indirectly) via a web-service (most probable a SOAP based web-service - located on a separate server from the calling app(s) ) - which means that there may be more than one app / instance attempting to connect to the singleton class. In PHP, what is the best way to create a global singleton or a web-service singleton? TIA

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  • How to comply with this guideline for submitting an application to the Software Center?

    - by George Edison
    I was reading through the Ubuntu Developer Programme Agreement for submitting applications to the Software Center and stubled across the following clause: 3.1 You must first test Apps you submit to confirm they are compatible with all currently supported versions of Ubuntu (as listed on Canonical's website at the date of submission by you) and your Apps must comply with the Publishing Policy. Does this mean I must install both the 32 and 64 bit versions of Ubuntu 8.04, 10.04, 10.10, 11.04, and 11.10? If so, that's 10 installations of Ubuntu - is that really feasible (even with virtual machines)? Alternatively, does anyone have suggestions for testing the application without actually installing each version? Some sort of chroot tool, perhaps?

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  • Advantages of Singleton Class over Static Class?

    Point 1)Singleton We can get the object of singleton and then pass to other methods.Static Class We can not pass static class to other methods as we pass objectsPoint 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed.Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use.Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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  • Advantages of Singleton Class over Static Class?

    Point 1) Singleton We can get the object of singleton and then pass to other methods. Static Class We can not pass static class to other methods as we pass objects Point 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed. Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use. Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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  • Creating HTML5 Offline Web Applications with ASP.NET

    - by Stephen Walther
    The goal of this blog entry is to describe how you can create HTML5 Offline Web Applications when building ASP.NET web applications. I describe the method that I used to create an offline Web application when building the JavaScript Reference application. You can read about the HTML5 Offline Web Application standard by visiting the following links: Offline Web Applications Firefox Offline Web Applications Safari Offline Web Applications Currently, the HTML5 Offline Web Applications feature works with all modern browsers with one important exception. You can use Offline Web Applications with Firefox, Chrome, and Safari (including iPhone Safari). Unfortunately, however, Internet Explorer does not support Offline Web Applications (not even IE 9). Why Build an HTML5 Offline Web Application? The official reason to build an Offline Web Application is so that you do not need to be connected to the Internet to use it. For example, you can use the JavaScript Reference Application when flying in an airplane, riding a subway, or hiding in a cave in Borneo. The JavaScript Reference Application works great on my iPhone even when I am completely disconnected from any network. The following screenshot shows the JavaScript Reference Application running on my iPhone when airplane mode is enabled (notice the little orange airplane):   Admittedly, it is becoming increasingly difficult to find locations where you can’t get Internet access. A second, and possibly better, reason to create Offline Web Applications is speed. An Offline Web Application must be downloaded only once. After it gets downloaded, all of the files required by your Web application (HTML, CSS, JavaScript, Image) are stored persistently on your computer. Think of Offline Web Applications as providing you with a super browser cache. Normally, when you cache files in a browser, the files are cached on a file-by-file basis. For each HTML, CSS, image, or JavaScript file, you specify how long the file should remain in the cache by setting cache headers. Unlike the normal browser caching mechanism, the HTML5 Offline Web Application cache is used to specify a caching policy for an entire set of files. You use a manifest file to list the files that you want to cache and these files are cached until the manifest is changed. Another advantage of using the HTML5 offline cache is that the HTML5 standard supports several JavaScript events and methods related to the offline cache. For example, you can be notified in your JavaScript code whenever the offline application has been updated. You can use JavaScript methods, such as the ApplicationCache.update() method, to update the cache programmatically. Creating the Manifest File The HTML5 Offline Cache uses a manifest file to determine the files that get cached. Here’s what the manifest file looks like for the JavaScript Reference application: CACHE MANIFEST # v30 Default.aspx # Standard Script Libraries Scripts/jquery-1.4.4.min.js Scripts/jquery-ui-1.8.7.custom.min.js Scripts/jquery.tmpl.min.js Scripts/json2.js # App Scripts App_Scripts/combine.js App_Scripts/combine.debug.js # Content (CSS & images) Content/default.css Content/logo.png Content/ui-lightness/jquery-ui-1.8.7.custom.css Content/ui-lightness/images/ui-bg_glass_65_ffffff_1x400.png Content/ui-lightness/images/ui-bg_glass_100_f6f6f6_1x400.png Content/ui-lightness/images/ui-bg_highlight-soft_100_eeeeee_1x100.png Content/ui-lightness/images/ui-icons_222222_256x240.png Content/ui-lightness/images/ui-bg_glass_100_fdf5ce_1x400.png Content/ui-lightness/images/ui-bg_diagonals-thick_20_666666_40x40.png Content/ui-lightness/images/ui-bg_gloss-wave_35_f6a828_500x100.png Content/ui-lightness/images/ui-icons_ffffff_256x240.png Content/ui-lightness/images/ui-icons_ef8c08_256x240.png Content/browsers/c8.png Content/browsers/es3.png Content/browsers/es5.png Content/browsers/ff3_6.png Content/browsers/ie8.png Content/browsers/ie9.png Content/browsers/sf5.png NETWORK: Services/EntryService.svc http://superexpert.com/resources/JavaScriptReference/ A Cache Manifest file always starts with the line of text Cache Manifest. In the manifest above, all of the CSS, image, and JavaScript files required by the JavaScript Reference application are listed. For example, the Default.aspx ASP.NET page, jQuery library, JQuery UI library, and several images are listed. Notice that you can add comments to a manifest by starting a line with the hash character (#). I use comments in the manifest above to group JavaScript and image files. Finally, notice that there is a NETWORK: section of the manifest. You list any file that you do not want to cache (any file that requires network access) in this section. In the manifest above, the NETWORK: section includes the URL for a WCF Service named EntryService.svc. This service is called to get the JavaScript entries displayed by the JavaScript Reference. There are two important things that you need to be aware of when using a manifest file. First, all relative URLs listed in a manifest are resolved relative to the manifest file. The URLs listed in the manifest above are all resolved relative to the root of the application because the manifest file is located in the application root. Second, whenever you make a change to the manifest file, browsers will download all of the files contained in the manifest (all of them). For example, if you add a new file to the manifest then any browser that supports the Offline Cache standard will detect the change in the manifest and download all of the files listed in the manifest automatically. If you make changes to files in the manifest (for example, modify a JavaScript file) then you need to make a change in the manifest file in order for the new version of the file to be downloaded. The standard way of updating a manifest file is to include a comment with a version number. The manifest above includes a # v30 comment. If you make a change to a file then you need to modify the comment to be # v31 in order for the new file to be downloaded. When Are Updated Files Downloaded? When you make changes to a manifest, the changes are not reflected the very next time you open the offline application in your web browser. Your web browser will download the updated files in the background. This can be very confusing when you are working with JavaScript files. If you make a change to a JavaScript file, and you have cached the application offline, then the changes to the JavaScript file won’t appear when you reload the application. The HTML5 standard includes new JavaScript events and methods that you can use to track changes and make changes to the Application Cache. You can use the ApplicationCache.update() method to initiate an update to the application cache and you can use the ApplicationCache.swapCache() method to switch to the latest version of a cached application. My heartfelt recommendation is that you do not enable your application for offline storage until after you finish writing your application code. Otherwise, debugging the application can become a very confusing experience. Offline Web Applications versus Local Storage Be careful to not confuse the HTML5 Offline Web Application feature and HTML5 Local Storage (aka DOM storage) feature. The JavaScript Reference Application uses both features. HTML5 Local Storage enables you to store key/value pairs persistently. Think of Local Storage as a super cookie. I describe how the JavaScript Reference Application uses Local Storage to store the database of JavaScript entries in a separate blog entry. Offline Web Applications enable you to store static files persistently. Think of Offline Web Applications as a super cache. Creating a Manifest File in an ASP.NET Application A manifest file must be served with the MIME type text/cache-manifest. In order to serve the JavaScript Reference manifest with the proper MIME type, I added two files to the JavaScript Reference Application project: Manifest.txt – This text file contains the actual manifest file. Manifest.ashx – This generic handler sends the Manifest.txt file with the MIME type text/cache-manifest. Here’s the code for the generic handler: using System.Web; namespace JavaScriptReference { public class Manifest : IHttpHandler { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/cache-manifest"; context.Response.WriteFile(context.Server.MapPath("Manifest.txt")); } public bool IsReusable { get { return false; } } } } The Default.aspx file contains a reference to the manifest. The opening HTML tag in the Default.aspx file looks like this: <html manifest="Manifest.ashx"> Notice that the HTML tag contains a manifest attribute that points to the Manifest.ashx generic handler. Internet Explorer simply ignores this attribute. Every other modern browser will download the manifest when the Default.aspx page is requested. Seeing the Offline Web Application in Action The experience of using an HTML5 Web Application is different with different browsers. When you first open the JavaScript Reference application with Firefox, you get the following warning: Notice that you are provided with the choice of whether you want to use the application offline or not. Browsers other than Firefox, such as Chrome and Safari, do not provide you with this choice. Chrome and Safari will create an offline cache automatically. If you click the Allow button then Firefox will download all of the files listed in the manifest. You can view the files contained in the Firefox offline application cache by typing about:cache in the Firefox address bar: You can view the actual items being cached by clicking the List Cache Entries link: The Offline Web Application experience is different in the case of Google Chrome. You can view the entries in the offline cache by opening the Developer Tools (hit Shift+CTRL+I), selecting the Storage tab, and selecting Application Cache: Notice that you view the status of the Application Cache. In the screen shot above, the status is UNCACHED which means that the files listed in the manifest have not been downloaded and cached yet. The different possible values for the status are included in the HTML5 Offline Web Application standard: UNCACHED – The Application Cache has not been initialized. IDLE – The Application Cache is not currently being updated. CHECKING – The Application Cache is being fetched and checked for updates. DOWNLOADING – The files in the Application Cache are being updated. UPDATEREADY – There is a new version of the Application. OBSOLETE – The contents of the Application Cache are obsolete. Summary In this blog entry, I provided a description of how you can use the HTML5 Offline Web Application feature in the context of an ASP.NET application. I described how this feature is used with the JavaScript Reference Application to store the entire application on a user’s computer. By taking advantage of this new feature of the HTML5 standard, you can improve the performance of your ASP.NET web applications by requiring users of your web application to download your application once and only once. Furthermore, you can enable users to take advantage of your applications anywhere -- regardless of whether or not they are connected to the Internet.

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  • Singleton constructor question

    - by gillyb
    Hi, I created a Singleton class in c#, with a public property that I want to initialize when the Singleton is first called. This is the code I wrote : public class BL { private ISessionFactory _sessionFactory; public ISessionFactory SessionFactory { get { return _sessionFactory; } set { _sessionFactory = value; } } private BL() { SessionFactory = Dal.SessionFactory.CreateSessionFactory(); } private object thisLock = new object(); private BL _instance = null; public BL Instance { get { lock (thisLock) { if (_instance == null) { _instance = new BL(); } return _instance; } } } } As far as I know, when I address the Instance BL object in the BL class for the first time, it should load the constructor and that should initialize the SessionFactory object. But when I try : BL.Instance.SessionFactory.OpenSession(); I get a Null Reference Exception, and I see that SessionFactory is null... why?

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  • Zend Framework - Database Table Singleton

    - by Sonny
    I have found myself doing this in my code to 'cache' the work done when instantiating my Zend_Db_Table models: if (Zend_Registry::isRegistered('x_table')) { $x_table = Zend_Registry::get('x_table'); } else { $x_table = new Default_Model_DbTable_X; Zend_Registry::set('x_table', $x_table); } It bothered me that this method isn't very DRY and it dawned on me today that a singleton pattern would probably be a better way to do this. Problem is, I've never written a singleton class. When I did some web searches, I found some offhand comments about Zend_Db_Table singletons, but no real examples. I already have meta-data caching configured. How do I make my Zend_Db_Table models singletons? Are there pitfalls or downsides?

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  • Is extending a singleton class wrong?

    - by Anwar Shaikh
    I am creating a logger for an application. I am using a third party logger library. In which logger is implemented as singleton. I extended that logger class because I want to add some more static functions. In these static functions I internally use the instance (which is single) of Logger(which i inherited). I neither creates instance of MyLogger nor re-implemented the getInstance() method of super class. But I am still getting warnings like destructor of MyLogger can not be created as parent class (Loggger) destructor is not accessible. I want to know, I am I doing something wrong? Inheriting the singleton is wrong or should be avoided??

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  • iphone singleton object synchronization

    - by user127091
    I'm working on an iphone app but this is probably a general question. I have a singleton Model class and there would be scenarios where multiple NSOperations (threads) would exist and work with the singleton object. If they all call the same method in this object, do i need to have some locking mechanism? Or can this method be executed only one at a time? I do not have a computer science background but my guess is that all threads would have their CALL to the same address (this method). Also can you please suggest a good beginner programming book that discusses general programming concepts. I don't have the brains for Knuth kinda books.

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  • Singleton design potential leak

    - by iBrad Apps
    I have downloaded a library off of github and have noticed that in the main singleton of the library there is a possible leak in this bit of code: +(DDGameKitHelper*) sharedGameKitHelper { @synchronized(self) { if (instanceOfGameKitHelper == nil) { [[DDGameKitHelper alloc] init]; } return instanceOfGameKitHelper; } return nil; } Now obviously there is no release or autorelease anywhere so I must do it but how and in what way properly? I have looked at various Singleton design patterns on the Internet and they just assign, in this case, instanceOfGameKitHelper to the alloc and init line. Anyway how would I properly fix this? Thanks!

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  • State management using the Application class in ASP.Net applications

    - by nikolaosk
    I have explained some of the state mechanisms that we have in our disposal for preserving state in ASP.Net applications in various posts in this blog. You can have a look at this post , this post , this post and this one . I have not presented yet an example in using the Application class/object for preserving state within our application. Application state is available globally in an application.The way we access Application State is through the HttpApplication object's Application property. Let...(read more)

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  • Windows Azure Learning Plan - Application Fabric

    - by BuckWoody
    This is one in a series of posts on a Windows Azure Learning Plan. You can find the main post here. This one deals with the Application Fabric for Windows Azure. It serves three main purposes - Access Control, Caching, and as a Service Bus.   Overview and Training Overview and general  information about the Azure Application Fabric, - what it is, how it works, and where you can learn more. General Introduction and Overview http://msdn.microsoft.com/en-us/library/ee922714.aspx Access Control Service Overview http://msdn.microsoft.com/en-us/magazine/gg490345.aspx Microsoft Documentation http://msdn.microsoft.com/en-gb/windowsazure/netservices.aspx Learning and Examples Sources for online and other Azure Appllications Fabric training Application Fabric SDK http://www.microsoft.com/downloads/en/details.aspx?FamilyID=39856a03-1490-4283-908f-c8bf0bfad8a5&displaylang=en Application Fabric Caching Service Primer http://blogs.msdn.com/b/appfabriccat/archive/2010/11/29/azure-appfabric-caching-service-soup-to-nuts-primer.aspx?wa=wsignin1.0 Hands-On Lab: Building Windows Azure Applications with the Caching Service http://www.wadewegner.com/2010/11/hands-on-lab-building-windows-azure-applications-with-the-caching-service/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+WadeWegner+%28Wade+Wegner+-+Technical%29 Architecture  Azure Application Fabric Internals and Architectures for Scale Out and other use-cases. Azure Application Fabric Architecture Guide http://blogs.msdn.com/b/yasserabdelkader/archive/2010/09/12/release-of-windows-server-appfabric-architecture-guide.aspx Windows Azure AppFabric Service Bus - A Deep Dive (Video) http://www.msteched.com/2010/Europe/ASI410 Access Control Service (ACS) High Level Architecture http://blogs.msdn.com/b/alikl/archive/2010/09/28/azure-appfabric-access-control-service-acs-v-2-0-high-level-architecture-web-application-scenario.aspx Applications  and Programming Programming Patterns and Architectures for SQL Azure systems. Various Examples from PDC 2010 on using Azure Application as a Service Bus http://tinyurl.com/2dcnt8o Creating a Distributed Cache using the Application Fabric http://blog.structuretoobig.com/post/2010/08/31/Creating-a-Poor-Mane28099s-Distributed-Cache-in-Azure.aspx  Azure Application Fabric Java SDK http://jdotnetservices.com/

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  • Advantages and disadvantages of building a single page web application

    - by ryanzec
    I'm nearing the end of a prototyping/proof of concept phase for a side project I'm working on, and trying to decide on some larger scale application design decisions. The app is a project management system tailored more towards the agile development process. One of the decisions I need to make is whether or not to go with a traditional multi-page application or a single page application. Currently my prototype is a traditional multi-page setup, however I have been looking at backbone.js to clean up and apply some structure to my Javascript (jQuery) code. It seems like while backbone.js can be used in multi-page applications, it shines more with single page applications. I am trying to come up with a list of advantages and disadvantages of using a single page application design approach. So far I have: Advantages All data has to be available via some sort of API - this is a big advantage for my use case as I want to have an API to my application anyway. Right now about 60-70% of my calls to get/update data are done through a REST API. Doing a single page application will allow me to better test my REST API since the application itself will use it. It also means that as the application grows, the API itself will grow since that is what the application uses; no need to maintain the API as an add-on to the application. More responsive application - since all data loaded after the initial page is kept to a minimum and transmitted in a compact format (like JSON), data requests should generally be faster, and the server will do slightly less processing. Disadvantages Duplication of code - for example, model code. I am going to have to create models both on the server side (PHP in this case) and the client side in Javascript. Business logic in Javascript - I can't give any concrete examples on why this would be bad but it just doesn't feel right to me having business logic in Javascript that anyone can read. Javascript memory leaks - since the page never reloads, Javascript memory leaks can happen, and I would not even know where to begin to debug them. There are also other things that are kind of double edged swords. For example, with single page applications, the data processed for each request can be a lot less since the application will be asking for the minimum data it needs for the particular request, however it also means that there could be a lot more small request to the server. I'm not sure if that is a good or bad thing. What are some of the advantages and disadvantages of single page web applications that I should keep in mind when deciding which way I should go for my project?

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  • game state singleton cocos2d, initWithEncoder always returns null

    - by taber
    Hi, I'm trying to write a basic test "game state" singleton in cocos2d, but for some reason upon loading the app, initWithCoder is never called. Any help would be much appreciated, thanks. Here's my singleton GameState.h: #import "cocos2d.h" @interface GameState : NSObject <NSCoding> { NSInteger level, score; Boolean seenInstructions; } @property (readwrite) NSInteger level; @property (readwrite) NSInteger score; @property (readwrite) Boolean seenInstructions; +(GameState *) sharedState; +(void) loadState; +(void) saveState; @end ... and GameState.m: #import "GameState.h" #import "Constants.h" @implementation GameState static GameState *sharedState = nil; @synthesize level, score, seenInstructions; -(void)dealloc { [super dealloc]; } -(id)init { if(!(self = [super init])) return nil; level = 1; score = 0; seenInstructions = NO; return self; } +(void)loadState { @synchronized([GameState class]) { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *saveFile = [documentsDirectory stringByAppendingPathComponent:kSaveFileName]; Boolean saveFileExists = [[NSFileManager defaultManager] fileExistsAtPath:saveFile]; if(!sharedState) { sharedState = [GameState sharedState]; } if(saveFileExists == YES) { [sharedState release]; sharedState = [[NSKeyedUnarchiver unarchiveObjectWithFile:saveFile] retain]; } // at this point, sharedState is null, saveFileExists is 1 if(sharedState == nil) { // this always occurs CCLOG(@"Couldn't load game state, so initialized with defaults"); sharedState = [self sharedState]; } } } +(void)saveState { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; NSString *saveFile = [documentsDirectory stringByAppendingPathComponent:kSaveFileName]; [NSKeyedArchiver archiveRootObject:[GameState sharedState] toFile:saveFile]; } +(GameState *)sharedState { @synchronized([GameState class]) { if(!sharedState) { [[GameState alloc] init]; } return sharedState; } return nil; } +(id)alloc { @synchronized([GameState class]) { NSAssert(sharedState == nil, @"Attempted to allocate a second instance of a singleton."); sharedState = [super alloc]; return sharedState; } return nil; } +(id)allocWithZone:(NSZone *)zone { @synchronized([GameState class]) { if(!sharedState) { sharedState = [super allocWithZone:zone]; return sharedState; } } return nil; } ... -(void)encodeWithCoder:(NSCoder *)coder { [coder encodeInt:level forKey:@"level"]; [coder encodeInt:score forKey:@"score"]; [coder encodeBool:seenInstructions forKey:@"seenInstructions"]; } -(id)initWithCoder:(NSCoder *)coder { CCLOG(@"initWithCoder called"); self = [super init]; if(self != nil) { CCLOG(@"initWithCoder self exists"); level = [coder decodeIntForKey:@"level"]; score = [coder decodeIntForKey:@"score"]; seenInstructions = [coder decodeBoolForKey:@"seenInstructions"]; } return self; } @end ... I'm saving the state on app exit, like this: - (void)applicationWillTerminate:(UIApplication *)application { [GameState saveState]; [[CCDirector sharedDirector] end]; } ... and loading the state when the app finishes loading, like this: - (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { ... [GameState loadState]; ... } I've tried moving around where I call loadState too, for example in my main CCScene, but that didn't seem to work either. Thanks again in advance.

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  • Rebinding and singleton-behaviour [NInject]

    - by Maximilian Csuk
    Hi! I have set up a NInject (using version 1.5) binding like this: Bind<ISessionFactory>().ToMethod<ISessionFactory>(ctx => { try { // create session factory, might fail because of database issues like wrong connection string } catch (Exception e) { throw new DatabaseException(e); } }).Using<SingletonBehavior>(); As you can see, this binding uses a singleton behavior but can also throw exception when something is not configured correctly, like a wrong connection string to the database. Now, when the creation of a session factory fails at first (throwing a database exception), NInject doesn't try to create the object again but always returns null. I would need NInject to check for null first and recreate when the instance is null, but of course not when there already is an instance successfully constructed (keeping it singleton). Like this: var a = Kernel.Get<ISessionFactory>(); // might fail, a = null // ... change some database settings var b = Kernel.Get<ISessionFactory>(); // might not fail anymore, b = ISessionFactory object Would I need to write a custom behavior or am I missing something else? Thanks for your answers!

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