四．享元模式实例分析（Example）
1、场景
一个文档
Document
中只有少数字符需要共享。结构
如下图所示
CharacterFactory
类
，享元工厂，用来创建和管理
Charactor
对象。如果请求的
Charactor
对象存在，怎返回已经存在的对象。否则新创建一个新的对象返回。
Character
类
：享元抽象类，通过这个接口，
Character
可以接受并作用与外部状态。
CharacterA /CharacterB/CharacterC 类 ：实现享元抽象类，为内部状态添加存储空间。
CharacterA /CharacterB/CharacterC 类 ：实现享元抽象类，为内部状态添加存储空间。
2、代码
|
1
、
字符工厂类CharacterFactory
|
|
class
CharacterFactory
{
private Dictionary
<char
, Character
> _characters = new Dictionary
<char
, Character
>();
public Character
GetCharacter(char
key)
{
// Uses "lazy initialization"
Character
character = null
;
if
(_characters.ContainsKey(key))
{
character = _characters[key];
}
else
{
switch
(key)
{
case 'A'
: character = new CharacterA
(); break
;
case 'B'
: character = new CharacterB
(); break
;
//...
case 'Z'
: character = new CharacterZ
(); break
;
}
_characters.Add(key, character);
}
return
character;
}
}
|
|
2
、
抽象数据对象类DataObject
及其具体实现类CustomersData
|
|
///
<summary>
///
The 'Flyweight' abstract class
///
</summary>
abstract
class Character
{
protected char
symbol;
protected int
width;
protected int
height;
protected int
ascent;
protected int
descent;
protected int
pointSize;
public abstract void
Display(int
pointSize);
}
///
<summary>
///
A 'ConcreteFlyweight' class
///
</summary>
class
CharacterA
: Character
{
public
CharacterA()
{
this
.symbol = 'A'
;
this
.height = 100;
this
.width = 120;
this
.ascent = 70;
this
.descent = 0;
}
public override void
Display(int
pointSize)
{
this
.pointSize = pointSize;
Console
.WriteLine(this
.symbol + " (pointsize "
+ this
.pointSize + ")"
);
}
}
///
<summary>
///
A 'ConcreteFlyweight' class
///
</summary>
class
CharacterB
: Character
{
public
CharacterB()
{
this
.symbol = 'B'
;
this
.height = 100;
this
.width = 140;
this
.ascent = 72;
this
.descent = 0;
}
public override void
Display(int
pointSize)
{
this
.pointSize = pointSize;
Console
.WriteLine(this
.symbol + " (pointsize "
+ this
.pointSize + ")"
);
}
}
// ... C, D, E, etc.
///
<summary>
///
A 'ConcreteFlyweight' class
///
</summary>
class
CharacterZ
: Character
{
// Constructor
public
CharacterZ()
{
this
.symbol = 'Z'
;
this
.height = 100;
this
.width = 100;
this
.ascent = 68;
this
.descent = 0;
}
public override void
Display(int
pointSize)
{
this
.pointSize = pointSize;
Console
.WriteLine(this
.symbol +" (pointsize "
+ this
.pointSize + ")"
);
}
}
|
|
3
、客户端代码
|
|
static
void Main
(string
[] args)
{
// Build a document with text
string
document = "AAZZBBZB"
;
char
[] chars = document.ToCharArray
();
CharacterFactory
factory = new CharacterFactory
();
// extrinsic state
int
pointSize = 10;
// For each character use a flyweight object
foreach
(char
c in
chars)
{
pointSize++;
Character
character = factory.GetCharacter(c);
character.Display(pointSize);
}
Console
.ReadKey();
}
|
3、实例运行结果
五、总结（Summary）
本文对享元模式（
Flyweight Pattern
）的概念、设计结构图、代码、使用场景、进行了描述。以一个享元模式实例进行了说明。如果一个应用程序使用了大量的对象，而大量的这些对象造成了很大的存储开销，这时可以考虑使用享元模式。
本文转自 灵动生活 51CTO博客，原文链接：http://blog.51cto.com/smartlife/269010，如需转载请自行联系原作者
