Design patterns, CAB & SCSF
Giới thiệu Composite Pattern
Composite UML class diagram (sử dụng abstract class)
Composite UML class diagram (sử dụng interface)
- Leaf là các đối tượng thành phần (hay còn gọi là Primitive).
- Component là giao diện cho các đối tượng thành phần, khai báo các method căn bản, là giao diện dùng khi access các thành phần.
- Composite định nghĩa các thao tác trên đối tượng thành phần, thực hiện lưu trữ và quản lý các đối tương thành phần.
Composite Pattern cho phép nhóm các object thành một single instance của một object. Các objects được nhóm có tính năng khá tương tự nhau. Object kết quả gọi là composite object. Việc thêm một component vào composite được hình dung tương tự việc thêm vào tree. Về kỹ thuật tất cả các Design patterns đều xoay quanh những tính năng của OOP encapsulation, inheritance, polymorphism...
Trong Composite kỹ thuật chính là polymorphism với 2 cách implement là polymorphism thông qua interface (recommended) và polymorphism qua abstract class.
Lab dành cho Composite Pattern
Ví dụ đơn giản khi có các region:
(England : (London : Chelsea )) và (France : Paris ) nhóm thành Europe , một region lớn hơn như sau:
(Europe: (
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Source code với C# (thực hiện qua interface)
Component.cs
-->
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Component interface
/// </summary>
interface Component
{
/// <summary>
/// Get the string of component (demo for component operation)
/// </summary>
///
/// String of component
/// </returns>
string operation();
/// <summary>
/// Get all children
/// </summary>
/// <returns>
/// List of <see cref="Component"/> children
/// </returns>
List<Component> getChildren();
/// <summary>
/// Add to children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
void add(Component c);
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// A bool value...
/// </returns>
bool remove(Component c);
}
}
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Composite.cs
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Composite
/// </summary>
class Composite : Component
{
/// <summary>
/// ID
/// </summary>
private string _id;
/// <summary>
/// Children collection
/// </summary>
private List<Component> _components = new List<Component>();
/// <summary>
/// Constructor
/// </summary>
/// <param name="id" type="string">
///
/// </param>
public Composite(string id)
{
_id = id;
}
#region [ INTERFACE IMPLEMENTATION ]
/// <summary>
/// Operation
/// </summary>
/// <returns>
/// A string value present name and list of children recursive
/// </returns>
public string operation()
{
string s = " (" + _id + ":";
this.getChildren().ForEach
(
delegate(Component child)
{
s += " " + child.operation();
}
);
return s + ") ";
}
/// <summary>
/// Implement interface get all children
/// </summary>
/// <returns>
/// List of <see cref="Component"/> children
/// </returns>
public List<Component> getChildren()
{
return _components;
}
/// <summary>
/// Add to children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
public void add(Component c)
{
_components.Add(c);
}
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// A bool value...
/// </returns>
public bool remove(Component c)
{
return _components.Remove(c);
}
#endregion
}
}
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Leaf.cs
-->
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Leaf
/// </summary>
class Leaf : Component
{
/// <summary>
///
/// </summary>
private string _id;
/// <summary>
/// Constructor
/// </summary>
/// <param name="id" type="string">
/// ID
/// </param>
public Leaf(string id)
{
_id = id;
}
#region [ INTERFACE IMPLEMENTATION ]
/// <summary>
///
/// </summary>
/// <returns>
/// A string value...
/// </returns>
public string operation()
{
return _id;
}
/// <summary>
/// Get all children
/// </summary>
/// <returns>
/// Just return null
/// </returns>
public List<Component> getChildren()
{
return null;
}
/// <summary>
/// Add to children collection, do nothing
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
public void add(Component c) { }
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// Just return false
/// </returns>
public bool remove(Component c) { return false; }
#endregion
}
}
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Program.cs
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Program
/// </summary>
class Program
{
/// <summary>
/// Main entry point
/// </summary>
/// <param name="args" type="string[]">
///
/// </param>
static void
{
//
Composite
//
Composite
london.add(new Leaf("
england.add(
//
Leaf
england.add(
england.remove(
//
Composite
france.add(new Leaf("
//
Composite europe = new Composite("
europe.add(
europe.add(
// Get
Console.WriteLine(europe.operation());
Console.ReadKey();
}
}
}
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Source code với C# (thực hiện qua abstract class)
Component.cs
-->
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Component interface
/// </summary>
public abstract class Component
{
/// <summary>
/// ID
/// </summary>
protected string _id;
/// <summary>
/// Constructor
/// </summary>
/// <param name="id" type="string">
///
/// </param>
public Component(string id)
{
_id = id;
}
/// <summary>
/// Get all children
/// </summary>
/// <returns>
/// List of <see cref="Component"/> children
/// </returns>
public abstract List<Component> getChildren();
/// <summary>
/// Get the string of component (demo for component operation)
/// </summary>
/// <returns>
/// String of component
/// </returns>
public abstract string operation();
/// <summary>
/// Add to children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
public abstract void add(Component c);
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// A bool value...
/// </returns>
public abstract bool remove(Component c);
}
}
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Composite.cs
-->
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Composite
/// </summary>
class Composite : Component
{
/// <summary>
/// Children collection
/// </summary>
private List<Component> _components = new List<Component>();
/// <summary>
/// Constructor
/// </summary>
/// <param name="id" type="string">
///
/// </param>
public Composite(string id)
: base(id)
{ }
#region [ OVERRIDE METHODS ]
/// <summary>
/// Operation
/// </summary>
/// <returns>
/// A string value present name and list of children recursive
/// </returns>
public override string operation()
{
string s = " (" + _id + ":";
this.getChildren().ForEach(delegate(Component child) { s += " " + child.operation(); });
return s + ") ";
}
/// <summary>
/// Implement interface get all children
/// </summary>
/// <returns>
/// List of <see cref="Component"/> children
/// </returns>
public override List<Component> getChildren()
{
return _components;
}
/// <summary>
/// Add to children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
public override void add(Component c)
{
_components.Add(c);
}
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// A bool value...
/// </returns>
public override bool remove(Component c)
{
return _components.Remove(c);
}
#endregion
}
}
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Leaf.cs
-->
using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatterns
{
/// <summary>
/// Leaf
/// </summary>
class Leaf : Component
{
/// <summary>
/// Constructor
/// </summary>
/// <param name="id" type="string">
/// ID
/// </param>
public Leaf(string id) : base(id) { }
#region [ OVERRIDE METHODS ]
/// <summary>
///
/// </summary>
/// <returns>
/// A string value...
/// </returns>
public override string operation()
{
return _id;
}
/// <summary>
/// Get all children
/// </summary>
/// <returns>
/// Just return null
/// </returns>
public override List<Component> getChildren()
{
return null;
}
/// <summary>
/// Add to children collection, do nothing
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to add
/// </param>
public override void add(Component c) { }
/// <summary>
/// Remove from children collection
/// </summary>
/// <param name="c" type="Component">
/// Child <see cref="Component"/> to remove
/// </param>
/// <returns>
/// Just return false
/// </returns>
public override bool remove(Component c) { return false; }
#endregion
}
}
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