singleton

问题 I have recently posted a similar question, but this is not a duplicate. Apologies for the code heavy post but I wanted to provide as much context as possible. I am having an issue with defining the analytics tool, 'Amplitude' as a service in my Angular.js application. Services are supposed to act as singletons throughout an application (source), so I am confused to be getting the following behavior. In my app.js file, I call AmplitudeService.logEvent('EVENT_NAME') in a .run function which

问题 I would like to convert a singleton-object programmatically into a Python module so that I can use the methods of this singleton-object directly by importing them via the module instead of accessing them as object attributes. By "programmatically" I mean that I do not want to have to copy-paste the class methods explicitly into a module file. I need some sort of a workaround that allows me to import the object methods into to global scope of another module. I would really appreciate if

问题 I have a singleton Session that I want instantiated at application launch. How do I do that? I'm using this method of creating the singleton: http://cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html 回答1: In the first line of your didFinishLaunchingWithOptions method - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { [YourSingletonClass class]; // ADD THIS LINE it will trigger initialize method initialization in

问题 I've been studying for a job interview and I've found this question: What's wrong with the following Singleton factory method getInstance()? public class Singleton { private static Singleton mySingleton; protected Singleton() {} public static Singleton getInstance() { if (mySingleton == null) { synchronized(Singleton.class) { if(mySingleton == null) { mySingleton = new Singleton(); } } } return mySingleton } } I know the constructor is wrong and should be private. However, they're asking

问题 Am I synchronizing on the same object instance in the following code? Can I do it safely? Class Sync {} Class A implements Runnable { void run() { synchronized(Sync.class) { System.out.println("I am synchronized"); } } } Class B implements Runnable { void run() { synchronized(Sync.class) { System.out.println("I too am synchronized"); } } } 回答1: You have to make a distinction between Loading of a Class and Resolving a Class . Class literals and the special method Class.forName(…) are different

问题 I have a function like this: $conf = array ('test_value' => 1, 'test_value2' => 2); function GetValueArray($array, $value) { return $array[$value]; } Im using this function to receive a value from an array. My problem is that i cannot use this function like this: GetValueArray('conf', 'test_value'); How could i convert 'conf' to the real array named conf to receive my 'test_value'? 回答1: Because functions have their own scope, be sure to 'globalize' the variable that you're looking into. But

问题 Trying to understand better about ember's register and inject. Basically my code looks like this: //creating a service Nerdeez.Wormhole = Ember.Object.extend({ ... }) //registering this service as a singleton App.register('wormhole:current', Nerdeez.Wormhole, {singleton: true}); //wanting to inject this service to be available everywhere in my application //especially in the adapter where i use it in the ajax hook App.inject('App', 'wormhole', 'wormhole:current'); //when trying to access this

问题 I used to use singleton get a single instance, but it was disclaimed by others because of some disadvantage in testing. What's the disadvantage? Is there any alternative good way for getting a global instance? So is it OK for me to create only one singleton class Global in application as global hub? so that I can put any other class's single instances in Global.Instance. 回答1: Ok, why singletons are bad you can read here: What is so bad about singletons? Specifically for testing: A typical

问题 I have the following setup: trait A { def doSomething(): Unit; } object B extends A { override def doSomething(): Unit = { // Implementation } } class B(creator: String) extends A { override def doSomething(): Unit = { B.doSomething() // Now this is just completely unnecessary, but the compiler of course insists upon implementing the method } } Now you may wonder why I even do this, why I let the class extend the trait as well. The problem is, that somewhere in the Program there is a

问题 I want to know how to inherit from a class 'BaseClient' that has a singleton and be able to use same instance of basic members from base class singleton in the inherited class too. public class BaseClient { protected string _url; protected string _username; protected string _password; private static BaseClient _instance; private static readonly object padlock = new object(); public static BaseClient Instance { get { lock (padlock) { if (_instance == null) { _instance = new BaseClient(true); }