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What is a singleton factory method?
Singleton – Ensures that at most only one instance of an object exists throughout application. Factory Method – Creates objects of several related classes without specifying the exact object to be created.
How do I create a new instance of singleton?
To create the singleton class, we need to have static member of class, private constructor and static factory method.
- Static member: It gets memory only once because of static, itcontains the instance of the Singleton class.
- Private constructor: It will prevent to instantiate the Singleton class from outside the class.
What is instance factory method?
A Factory Pattern or Factory Method Pattern says that just define an interface or abstract class for creating an object but let the subclasses decide which class to instantiate. In other words, subclasses are responsible to create the instance of the class.
Can a factory be static?
No, factory class by default shouldn’t be static. Actually, static classes are not welcomed in OOP world since they can also convey some state and therefore introduce global application state. If you need only one factory object to be present, you can control it’s creation through singleton pattern.
How is a singleton used in a factory pattern?
Singleton returns the same instance of class all the time, factory can create objects by instantiating various classes, or by using other allocation schemes such as an object pool. so singleton can be used in factory pattern
How to create a singleton instance in C #?
This calls for inversion of control. Just start by adding an interface to SomeSingleton say ISomeSingleton. Then all consumers of ISomeSingleton will just get an constructor parameter of ISomeSingleton. When no consumer calls the SomeSingleton directly you can just remove it.
When to use lazy initialization to create a singleton?
If two threads are going to execute the creation method at the same time when a singleton does not yet exist, they both must check for an instance of the singleton and then only one should create the new one. The lazy initialization will create the singleton object only if is necessary.
How does the factory check if a singleton is null?
The one expression of the factory checks if _instance is null, and if it is, it returns the result of Singleton._internal (), which sets the static _instance to the singleton’s reference. If _instance has been set by a previous call to Singleton._internal (), the cached instance is returned instead. Elegant!