Factory method
Its a Creational design pattern.
Definition: “The factory pattern is used to replace class constructors, abstracting the process of object generation so that the type of the object instantiated can be determined at run-time.”
Define an interface for creating an object, but let the classes that implement the interface decide which class to instantiate. The Factory method lets a class defer instantiation to subclasses.
Easy way
easily we can say that it’s a method that provides the object of a class at run time. Normally it happens by passing argument to that method and on the basis of that argument method decide which object to create.
Example :-
You have ice-cream factory and having two flaour and want to add one more . task of this method (Factory) will be to fulfill the desired demand that a customer makes. So basically Factory Method Pattern is just a method which actually fulfills our demand of object creation at run-time.
Same like for shape also See below UML diagram source http://www.tutorialspoint.com
Code in JAVA
Here are classes
interface IShape
{
string draw();
}
class Circle: IShape
{
public string draw()
{
return "Circle";
}
}
class Rectangle : IShape
{
public string Functionality()
{
return "Rectangle";
}
}
class Square : IShape
{
public string Functionality()
{
return "Square";
}
}
Factory method
static class Factory
{
/// This is the Factory method
public static IShape Get(int id)
{
switch (id)
{
case 0:
return new Circle();
case 1:
return new Rectangle();
case 2:
return new Square();
default:
return null;
}
}
}
Factory method is just like regular method but when we are talking about patterns it just returns the instance of a class at run-time depending upon the input method gets.
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