singleton

PHP Extending class makes children inherit same static property

由 爷，独闯天下 提交于 2019-12-08 00:25:07
问题 I'd like to start by showing a test case: class A { public static $instance=null; public function __construct(){ self::$instance=$this; } public function className(){ return get_class(self::$instance); } } class B extends A { public function className(){ return get_class(self::$instance); } } // test code $b=new B(); echo $b->className; // B $a=new A(); echo $a->className; // A echo $b->className; // A <- error: not B any more! Notes I'm using a factory+singleton patterns above. Well,

How to answer the interview question: What is a singleton and how would you use one? [closed]

由 喜夏-厌秋 提交于 2019-12-07 21:52:25
问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 8 years ago . I've read the questions on S.O. regarding Singleton and just watched an hour long google tech talk. As far as I can tell, the

Spark Object (singleton) serialization on executors

由 人盡茶涼 提交于 2019-12-07 20:06:33
问题 I am not sure that what I want to achieve is possible. What I do know is I am accessing a singleton object from an executor to ensure it's constructor has been called only once on each executor. This pattern is already proven and works as expected for similar use cases in my code base. However, What I would like to know is if I can ship the object after it has been initialized on the driver. In this scenario, when accesing ExecutorAccessedObject.y , ideally it would not call the println but

Spring singleton bean 与 prototype bean 的依赖

由 我怕爱的太早我们不能终老 提交于 2019-12-07 19:10:38
本文同步至： http://www.waylau.com/spring-singleton-beans-with-prototype-bean-dependencies/ ##问题 我们知道，Spring bean 默认的 scope 是 singleton（单例），但有些场景（比如多线程）需要每次调用都生成一个实例， 此时 scope 就应该设为 prototype。如： <!-- more --> @Component @Scope("prototype") public class DadTask implements Runnable { static Logger logger = Logger.getLogger(DadTask.class); @Autowired DadDao dadDao; private String name; /** * */ public DadTask setDadTask(String name) { this.name = name; return this; } /* (non-Javadoc) * @see java.lang.Runnable#run() */ @Override public void run() { logger.info("DadTask:"+this + ";DadDao:"+dadDao + ";"

Delegate not working in singleton [closed]

由 限于喜欢 提交于 2019-12-07 18:04:52
问题 This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center. Closed 6 years ago . To have a network connection over my multiple view's, I created a Singleton network controller to handle the data between the server and the client.

How static vs singleton classes work (databases)

由 夙愿已清 提交于 2019-12-07 17:25:10
问题 I am confused on how a singleton model vs a static model works for database connections. My friend created a "static" class and showed me it but it did not make any sense on how it was static. I kind of understand the singleton method of how to create a database connection, but i'm not sure it meets my goal. The main thing I want to do is cut down on the number of connections opened to MYSQL. I have a class with a function that calls the database quiet frequently, and there is no reason for

What is the correct way of ensuring a single instance of a class? [duplicate]

由 馋奶兔 提交于 2019-12-07 16:21:23
问题 This question already has answers here : What is the correct way to write a singleton pattern in Ruby? (3 answers) What is an efficient way to implement a singleton pattern in Java? [closed] (29 answers) Closed last year . In java I would create something like this: private static MyClass instance; public static MyClass getInstance() { if(instance != null) { return instance; } instance = new MyClass(); return instance; } What is the appropriate way to obtain the same functionality in ruby?

Android - using Singleton to access hold application settings, and Context

由 那年仲夏 提交于 2019-12-07 16:05:41
I need to access settings from various activities in my Android app. Rather than messing around with SharedPreferences in various activities I want to create a Singleton class, and grab all the settings at once using SharedPreferences in the Singleton. I also want a method in the Singleton to save settings where required, again using SharedPreferences. The trouble with this is that I need an Activity context to use SharedPreferences. Could I pass this into the Singleton.. I've read about memory leaks and am wary of doing this. Or am I completely barking up the wrong tree and is there a better

Copy/Inheritance of Ruby Matrix class (core/std lib)

由 核能气质少年 提交于 2019-12-07 13:43:05
问题 I tried to extend an existing Singleton class in Ruby, as an example the Matrix class. My first quick&dirty solution was a monkey patch (reopen class and extend with functionality). But I think, monkey patching in general isn't good, especially if someone tries to overwrite basic methods of core classes like in String, Integer, ... Next step was to find out, how I can get a real hard copy of the Matrix class with a new name (like MatrixExt) which behaves as a standalone singleton. MatrixExt =

Singleton Pattern with Public Constructor

由 核能气质少年 提交于 2019-12-07 13:41:59
问题 public class MySingletonClass { public MySingletonClass() { _mySingletonObj = Instance(); } public static MySingletonClass Instance() { if (_mySingletonObj == null) { lock (typeof(lockObject)) { if (_mySingletonObj == null) _mySingletonObj = new MySingletonClass(); } } return _mySingletonObj ; } } MySingletonClass _myObj = new MySingletonClass(); This act as singleton with public constructors..? Thanks 回答1: No, it's not a singleton - anyone can create multiple instances of it. (Leaving aside
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