The Bridge design pattern decouples an abstraction from its implementation so that the two can vary independently.
A visualization of the classes and objects participating in this pattern.
The classes and objects participating in this pattern include:
BusinessObject)
CustomersBusinessObject)
DataObject)
CustomersDataObject)
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.
copyusing System;
namespace Bridge.Structural
{
/// <summary>
/// Bridge Design Pattern
/// </summary>
public class Program
{
public static void Main(string[] args)
{
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>
public class Abstraction
{
protected Implementor implementor;
public Implementor Implementor
{
set { implementor = value; }
}
public virtual void Operation()
{
implementor.Operation();
}
}
/// <summary>
/// The 'Implementor' abstract class
/// </summary>
public abstract class Implementor
{
public abstract void Operation();
}
/// <summary>
/// The 'RefinedAbstraction' class
/// </summary>
public class RefinedAbstraction : Abstraction
{
public override void Operation()
{
implementor.Operation();
}
}
/// <summary>
/// The 'ConcreteImplementorA' class
/// </summary>
public class ConcreteImplementorA : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorA Operation");
}
}
/// <summary>
/// The 'ConcreteImplementorB' class
/// </summary>
public class ConcreteImplementorB : Implementor
{
public override void Operation()
{
Console.WriteLine("ConcreteImplementorB Operation");
}
}
}
This real-world code demonstrates the Bridge pattern in which a BusinessObject abstraction is decoupled from the implementation in DataObject. The DataObject implementations can evolve dynamically without changing any clients.
using System;
using System.Collections.Generic;
namespace Bridge.RealWorld
{
/// <summary>
/// Bridge Design Pattern
/// </summary>
public class Program
{
public static void Main(string[] args)
{
// Create RefinedAbstraction
var customers = new Customers();
// Set ConcreteImplementor
customers.Data = new CustomersData("Chicago");
// 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>
public class CustomersBase
{
private DataObject dataObject;
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()
{
dataObject.ShowAllRecords();
}
}
/// <summary>
/// The 'RefinedAbstraction' class
/// </summary>
public class Customers : CustomersBase
{
public override void ShowAll()
{
// Add separator lines
Console.WriteLine();
Console.WriteLine("------------------------");
base.ShowAll();
Console.WriteLine("------------------------");
}
}
/// <summary>
/// The 'Implementor' abstract class
/// </summary>
public 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 string GetCurrentRecord();
public abstract void ShowRecord();
public abstract void ShowAllRecords();
}
/// <summary>
/// The 'ConcreteImplementor' class
/// </summary>
public class CustomersData : DataObject
{
private readonly List<string> customers = new List<string>();
private int current = 0;
private string city;
public CustomersData(string city)
{
this.city = city;
// 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 string GetCurrentRecord()
{
return customers[current];
}
public override void ShowRecord()
{
Console.WriteLine(customers[current]);
}
public override void ShowAllRecords()
{
Console.WriteLine("Customer City: " + city);
foreach (string customer in customers)
{
Console.WriteLine(" " + customer);
}
}
}
}
The .NET optimized code demonstrates the
same real-world situation as above but uses modern, built-in .NET features,
such as, generics, reflection, LINQ, lambda functions, etc.
You can find an example on our Singleton pattern page.
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