簡述：

　　享元模式：運用共享技術有效地支援大量細粒度的物件。

　　享元模式包括：享元工廠類、享元介面類、具體享元類

　　　　享元工廠類：　用來建立並管理享元介面類物件，它主要使用來確保合理地共享享元介面類，當用戶請求一個享元介面類物件時，享元工廠類物件提供一個已建立的例項或者建立一個（不存在的話）

　　　　享元介面類：所有具體享元類的超類或介面，通過這個介面可以接受並作用於外部狀態。

　　　　具體享元類：指那些不需要共享的享元介面類的子類，因為享元介面類共享成為可能，但它並不強制共享。

享元模式：

 1 #include <iostream>
 2 #include <map>
 3
 
 using namespace std;
 4 
 5 // 享元介面類
 6 class CFlyweight
 7 {
 8 public:
 9     virtual void Operation(int nExtrinsicstate) = 0;
10 };
11 
12 // 具體享元類
13 class CConcreteFlyweight : public CFlyweight
14 {
15 public:
16     virtual void Operation(int nExtrinsicstate) { cout << "具體Flyweight：" << nExtrinsicstate << endl; }
 
17 };
18 
19 // 不需要共享的享元子類
20 class CUnsharedConcreteFlyWeight : public CFlyweight
21 {
22 public:
23     virtual void Operation(int nExtrinsicstate) { cout << "不共享的具體Flyweight：" << nExtrinsicstate << endl; }
24 };
25 
26 // 享元工廠類
27 class CFlyweightFactory
28 {
29 private:
30     map<string
 
, CFlyweight*> m_mapFlyweights;
31 
32 public:
33     CFlyweightFactory()
34     {
35         m_mapFlyweights.insert(make_pair("X", new CConcreteFlyweight()));
36         m_mapFlyweights.insert(make_pair("Y", new CConcreteFlyweight()));
37         m_mapFlyweights.insert(make_pair("Z", new CConcreteFlyweight()));
38     }
39 
40     ~CFlyweightFactory()
41     {
42         map<string, CFlyweight*>::iterator ite = m_mapFlyweights.begin();
43         while (ite != m_mapFlyweights.end())
44         {
45             if((*ite).second)
46             {
47                 delete (*ite).second;
48                 (*ite).second = NULL;
49             }
50                 
51             ++ite;
52         }
53 
54         m_mapFlyweights.clear();
55     }
56 
57     CFlyweight* GetFlyweight(string szKey) { return m_mapFlyweights[szKey]; }
58 };
59 
60 
61 int main()
62 {
63     int nExtrinsicstate = 22;
64 
65     CFlyweightFactory FlyweightFactory;
66 
67     CFlyweight* fx = FlyweightFactory.GetFlyweight("X");
68     fx->Operation(--nExtrinsicstate);
69 
70     CFlyweight* fy = FlyweightFactory.GetFlyweight("Y");
71     fy->Operation(--nExtrinsicstate);
72 
73     CFlyweight* fz = FlyweightFactory.GetFlyweight("Z");
74     fz->Operation(--nExtrinsicstate);
75 
76     CUnsharedConcreteFlyWeight uf;
77     uf.Operation(--nExtrinsicstate);
78 
79     system("pause");
80     return 0;
81 }

輸出結果：

例：網站共享程式碼

程式碼如下：

 1 #include <iostream>
 2 #include <map>
 3 using namespace std;
 4 
 5 // 使用者類
 6 class CUser
 7 {
 8 private:
 9     string m_szName;
10 
11 public:
12     CUser(string szName) { m_szName = szName; }
13 
14     string GetName() { return m_szName; }
15 };
16 
17 // 網站基類（享元介面類）
18 class CWebSite
19 {
20 public:
21     virtual void Use(CUser* pUser) = 0;
22 };
23 
24 // 具體網站類（具體享元類）
25 class CConcreteWebSite : public CWebSite
26 {
27 private:
28     string m_szName;
29 
30 public:
31     CConcreteWebSite(string szName) { m_szName = szName; }
32 
33     virtual void Use(CUser* pUser) { cout << "網站分類： " + m_szName << " 使用者： " + pUser->GetName() << endl; }
34 };
35 
36 // 網站工廠類（享元工廠類）
37 class CWebSiteFactory
38 {
39 private:
40     map<string, CWebSite*> m_mapWebSites;
41 
42 public:
43     ~CWebSiteFactory()
44     {
45         map<string, CWebSite*>::iterator ite = m_mapWebSites.begin();
46         while (ite != m_mapWebSites.end())
47         {
48             if ((*ite).second)
49             {
50                 delete (*ite).second;
51                 (*ite).second = NULL;
52             }
53             ++ite;
54         }
55         m_mapWebSites.clear();
56     }
57 
58     // 獲得網站分類
59     CWebSite* GetWebSiteCategory(string szKey)
60     {
61         if (!m_mapWebSites[szKey])
62             m_mapWebSites[szKey] = new CConcreteWebSite(szKey);
63 
64         return m_mapWebSites[szKey];
65     }
66 
67     // 獲得網站分類總數
68     int GetWebSiteCount() { return m_mapWebSites.size(); }
69 };
70 
71 
72 int main()
73 {
74     CWebSiteFactory WebSiteFactory;
75 
76     CWebSite* fx = WebSiteFactory.GetWebSiteCategory("產品展示");
77     fx->Use(&CUser("GHL"));
78 
79     CWebSite* fy = WebSiteFactory.GetWebSiteCategory("產品展示");
80     fy->Use(&CUser("GGG"));
81 
82     CWebSite* fz = WebSiteFactory.GetWebSiteCategory("產品展示");
83     fz->Use(&CUser("HHH"));
84 
85     CWebSite* fl = WebSiteFactory.GetWebSiteCategory("部落格");
86     fl->Use(&CUser("LLL"));
87 
88     CWebSite* fm = WebSiteFactory.GetWebSiteCategory("部落格");
89     fm->Use(&CUser("ggg"));
90 
91     CWebSite* fn = WebSiteFactory.GetWebSiteCategory("部落格");
92     fn->Use(&CUser("hhh"));
93 
94     cout << "網站分類總數為： " << WebSiteFactory.GetWebSiteCount() << endl;
95 
96     system("pause");
97     return 0;
98 }