singleton

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: cracking singleton with other ways Can anyone please tell me when a Singleton would not work as a Singleton ? 回答1: There is very good post published on Sun website by author Joshua Fox . Please go through this. below are some of them scenario when your Singleton doesn't behave like. Multiple Singletons in Two or More Virtual Machines Multiple Singletons Simultaneously Loaded by Different Class Loaders Singleton

问题 I recently read somewhere that the special value None in python is a singleton object of its own class, specifically NoneType . This explained a lot, since most errors involving None in python produce AttributeError s instead of some special "NoneError" or something. Since all of these AttributeErrors reflected the attributes that NoneType lacked, I became intrigued by what attributes NoneType did have, if any. I decided to look into this NoneType and learn more about it. I've always found

问题 How do I reset a singleton object in Ruby? I know that one'd never want to do this in real code but what about unit tests? Here's what I am trying to do in an RSpec test - describe MySingleton, "#not_initialised" do it "raises an exception" do expect {MySingleton.get_something}.to raise_error(RuntimeError) end end It fails because one of my previous tests initialises the singleton object. I have tried following Ian White's advice from this link which essentially monkey patches Singleton to

问题 I am trying to mock a Scala singleton object. In particular, I need to mock the object play.api.libs.ws.WS used inside a service component (class under test). Using Mockito this is not possible, the test execution fails in the following way: [error] MockitoException: : [error] Cannot mock/spy class play.api.libs.ws.WS$ [error] Mockito cannot mock/spy following: [error] - final classes [error] - anonymous classes [error] - primitive types (GeolocationSpec.scala:18) Reading here, it seems that

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before

问题 My persons class: public class User { public int Id { get; private set; } public string Isim { get; set; } public string Soyad { get; set; } public User(string isim, string soyad) { Isim = isim; Soyad = soyad; } } My UserBusiness class: public sealed class UserBusiness { JuqueryDbEntities entity = new JuqueryDbEntities(); private static volatile UserBusiness instance; private static readonly object syncRoot = new Object(); private UserBusiness() { } public static UserBusiness Instance { get {