singleton

问题 As you can see from my nickname I'm newbie actually learning about Singleton pattern, where I got one problem. Before I've learned that static constructors are always executed before the standard constructors, but in this code below, the result is different, first I see the "Insta" string then the "Static", why does it happen ? sealed class Singleton { private static readonly Singleton instance; private Singleton() { Console.WriteLine("Insta"); } static Singleton() { instance = new Singleton(

问题 I've implemented a singleton class and keep getting the warning that a method I'm writing is a 'new protected member declared in a seal class.' It's not affecting the build but I don't really want to ignore the warning in case it causes problems later on? I understand a sealed class is a class that cannot be inherited - so it's methods cannot be overridden, but I still don't get why the following code would give me the warning (is it due to the use of the singleton design?): namespace

问题 I am creating a Service in which there are three Threads : GPS location tracker that will write location values into a database. Sender Thread that both reads and writes into the database. Receiver thread that too reads and writes to the database. Now I have seen posts like these in which it is said that only one Helper class should be available as well as only on DB connection. I have tried to implement only one instance of the Helper class by using the Singleton pattern however I am utterly

问题 This question already has answers here : Objective-C: Use singleton vs. use class as an object? (3 answers) Closed 5 years ago . It seems we always use a sharedInstance class variable to access the Singleton and perform methods on it. But why don't we just make all operations class methods and not have a variable to deal with at all? [SingletonClass uploadFile:(NSFile *)file] instead of [[SingletonClass sharedInstance] uploadFile:(NSFile *)file] (or the Swift equivalent). What benefits do the

问题 The script: app = angular.module('app', []) app.factory 'MyFactory', -> val: 'Clark Kent' app.controller 'MainCtrl', ($scope, MyFactory) -> MyFactory.val = 'Waldo' $scope.myFactory = MyFactory Put this in the console: angular.injector(['ng','app']).invoke(function(MyFactory) { console.log(MyFactory); }) ... and instead of Waldo , you get Clark Kent !! Why doesn't it return the same object? Check out the plunkr 回答1: Services in Angular are singletons in the sense that they are only created

问题 The following snippet is straight forward, public MyClass getInstance() { if(uniqueInstance == null) { uniqueInstance = new MyClass(); } return uniqueInstance; } What does the following one do? public MyClass getInstance() { if(uniqueInstance == null) { synchronized(MyClass.class) { uniqueInstance = new MyClass(); } } return uniqueInstance; } 回答1: It's a poor attempt to make it threadsafe to prevent a race condition caused by at least two threads which have simultaneously entered the if block

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 6 years ago . I am writing a module with method foo , which calls a class method bar on the receiver's class. My current approach is to use self.class.bar , which works fine unless the class method is defined in an instance

问题 I make a lot of "design your own ____" applications. What I do is I make a singleton class to hold all the customizations the user has chosen. For example: When you select you want something green, it updates a getter/setter in the singleton to be green. Then when the application needs to know what color was selected it gets the info from the same getter/setter. The way I used to do this was by storing the information in the UI (just checking what color was selected from the drop-down). After

问题 I want to implement Thread Safe Lazily Loaded Singleton in Java. Is this a good design? public final class ThreadSafeLazySynchronizedSingleton { private ThreadSafeLazySynchronizedSingleton(){} private static ThreadSafeLazySynchronizedSingleton instance; public static ThreadSafeLazySynchronizedSingleton getSynchronizedInstance(){ synchronized(ThreadSafeLazySynchronizedSingleton.class){ if (instance==null){ instance = new ThreadSafeLazySynchronizedSingleton(); } return instance; } } } I also

问题 I have an android project where i have different objects that one or more of my activities need to acess now i was thinking of creating a subclass of Application however under the documentation of Application it states the following: There is normally no need to subclass Application. In most situation, static singletons can provide the same functionality in a more modular way. If your singleton needs a global context (for example to register broadcast receivers), the function to retrieve it