Prototype - Harsh4999/Design-Patterns GitHub Wiki

Use

• Whenever we want to ignore creation of object of some type in order to save cost or memory or some performance we use prototype.
• They help us create copies of existing instance and saves us from recreating the objects from scratch

Uml

• Prototype Abstract is a class whos object will serve as prototype of our use.
• Prototype has a method clone
• Concrete Prototype will be used to override the clone method as per needs
• Client/Director will use prototypes to clone the classes

Implementation

• We start by creating a class which will be a prototype (indicate that cloning is supported)
• Class must implement cloneable interface
• Clss should have override clone method and return a copy of itself
• Method should declare CloneNotSupportedException in throws to give subclasses a chance to decide on whether to support clonning or not
• While implementing Clone method we should consider the deep copy & shallow copy and choose which ever is applicable
• We also need to implement initialize method in the prototype class
• If the object which we are cloning is immutable use shallow copy else deep copy
• We should always provide reset method to reset cloned state
• Its usefull when we have a large object
• Prototype registry is a class in which we can register the main instance of the prototype and later on from registry we can clone the prototype
• Eg: Object.clone()
• Example code here