This structural code demonstrates the Bridge pattern which separates (decouples) the interface from its implementation. The implementation can evolve without changing clients which use the abstraction of the object.
// Bridge pattern -- Structural example
using System;
namespace DoFactory.GangOfFour.Bridge.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Bridge Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
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.ReadKey();
}
}
/// <summary>
/// The 'Abstraction' class
/// </summary>
class Abstraction
{
protected Implementor implementor;
// Property
public Implementor Implementor
{
set { implementor = value; }
}
public virtual void Operation()
{
implementor.Operation();
}
}
/// <summary>
/// The 'Implementor' abstract class
/// </summary>
abstract class Implementor
{
public abstract void Operation();
}
/// <summary>
/// The 'RefinedAbstraction' class
/// </summary>
class RefinedAbstraction : Abstraction
{
public override void Operation()
{
implementor.Operation();
}
}
/// <summary>
/// The 'ConcreteImplementorA' class
/// </summary>
class ConcreteImplementorA : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorA Operation");
}
}
/// <summary>
/// The 'ConcreteImplementorB' class
/// </summary>
class ConcreteImplementorB : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorB Operation");
}
}
} // Bridge pattern -- Real World example
using System;
using System.Collections.Generic;
namespace DoFactory.GangOfFour.Bridge.RealWorld
{
/// <summary>
/// MainApp startup class for Real-World
/// Bridge Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Create RefinedAbstraction
Customers customers = new Customers("Chicago");
// Set ConcreteImplementor
customers.Data = new CustomersData();
// Exercise the bridge
customers.Show();
customers.Next();
customers.Show();
customers.Next();
customers.Show();
customers.Add("Henry Velasquez");
customers.ShowAll();
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Abstraction' class
/// </summary>
class CustomersBase
{
private DataObject _dataObject;
protected string group;
public CustomersBase(string group)
{
this.group = group;
}
// Property
public DataObject Data
{
set { _dataObject = value; }
get { return _dataObject; }
}
public virtual void Next()
{
_dataObject.NextRecord();
}
public virtual void Prior()
{
_dataObject.PriorRecord();
}
public virtual void Add(string customer)
{
_dataObject.AddRecord(customer);
}
public virtual void Delete(string customer)
{
_dataObject.DeleteRecord(customer);
}
public virtual void Show()
{
_dataObject.ShowRecord();
}
public virtual void ShowAll()
{
Console.WriteLine("Customer Group: " + group);
_dataObject.ShowAllRecords();
}
}
/// <summary>
/// The 'RefinedAbstraction' class
/// </summary>
class Customers : CustomersBase
{
// Constructor
public Customers(string group)
: base(group)
{
}
public override void ShowAll()
{
// Add separator lines
Console.WriteLine();
Console.WriteLine("------------------------");
base.ShowAll();
Console.WriteLine("------------------------");
}
}
/// <summary>
/// The 'Implementor' abstract class
/// </summary>
abstract class DataObject
{
public abstract void NextRecord();
public abstract void PriorRecord();
public abstract void AddRecord(string name);
public abstract void DeleteRecord(string name);
public abstract void ShowRecord();
public abstract void ShowAllRecords();
}
/// <summary>
/// The 'ConcreteImplementor' class
/// </summary>
class CustomersData : DataObject
{
private List<string> _customers = new List<string>();
private int _current = 0;
public CustomersData()
{
// Loaded from a database
_customers.Add("Jim Jones");
_customers.Add("Samual Jackson");
_customers.Add("Allen Good");
_customers.Add("Ann Stills");
_customers.Add("Lisa Giolani");
}
public override void NextRecord()
{
if (_current <= _customers.Count - 1)
{
_current++;
}
}
public override void PriorRecord()
{
if (_current > 0)
{
_current--;
}
}
public override void AddRecord(string customer)
{
_customers.Add(customer);
}
public override void DeleteRecord(string customer)
{
_customers.Remove(customer);
}
public override void ShowRecord()
{
Console.WriteLine(_customers[_current]);
}
public override void ShowAllRecords()
{
foreach (string customer in _customers)
{
Console.WriteLine(" " + customer);
}
}
}
} 