Programming - Bridge Structural Design Pattern

Decouple an abstraction from its implementation so that the two can vary independently.

The classes and/or objects participating in this pattern are:

Abstractionand
and and
- defines the abstraction's interface.
- maintains a reference to an object of type Implementor.
RefinedAbstractionand
and
- extends the interface defined by Abstraction.
Implementorand
and and
- defines the interface for implementation classes. This interface doesn't have to correspond exactly to Abstraction's interface; in fact the two interfaces can be quite different. Typically the Implementation interface provides only primitive operations, and Abstraction defines higher-level operations based on these primitives.
ConcreteImplementor
- implements the Implementor interface and defines its concrete implementation.

// Bridge pattern -- Structural example

                using
              
              System;

               namespace

DoFactory.GangOfFour.Bridge.Structural
{

// MainApp test application

class MainApp
{
static void Main()
{
Abstraction ab = new RefinedAbstraction();

// Set implementation and call
ab.Implementor = new ConcreteImplementorA();
ab.Operation();

// Change implemention and call
ab.Implementor = new ConcreteImplementorB();
ab.Operation();

// Wait for user
Console.Read();
}
}

// "Abstraction"

class Abstraction
{
protected Implementor implementor;

// Property
public Implementor Implementor
{
set{ implementor = value; }
}

public virtual void Operation()
{
implementor.Operation();
}
}

// "Implementor"

abstract class Implementor
{
public abstract void Operation();
}

// "RefinedAbstraction"

class RefinedAbstraction : Abstraction
{
public override void Operation()
{
implementor.Operation();
}
}

// "ConcreteImplementorA"

class ConcreteImplementorA : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorA Operation");
}
}

// "ConcreteImplementorB"

class ConcreteImplementorB : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorB Operation");
}
}
}

and

Output expected:

              ConcreteImplementorA Operation

               ConcreteImplementorB Operation