組合模式(Composite Pattern)

時間 2019-12-10

標籤組合模式 composite pattern 简体版

原文原文鏈接

組合模式概述

定義：組合多個對象造成樹形結構以表示具備部分-總體關係的層次結構。組合模式讓客戶端能夠統一對待單個對象和組合對象。又被成爲「部分-總體」(Part-Whole)模式，屬於對象結構性模式安全

定義什麼的，最枯燥了。簡單的來講，就如咱們鼠標右擊新建文件夾同樣，在一個磁盤裏，咱們能夠新建一個文件夾A，也能夠新建某個類型的文件a，A和a都在同一目錄下，固然，咱們也能夠點擊進入文件夾A，在A中新建新的文件夾B，也能夠在A中新建文件b。只要是文件夾，就能夠在裏面繼續新建文件夾和文件，而文件則只能用來放數據，不能在新建了。ide

固然，也能夠經過win+r調出運行，輸入cmd(commmand),進入你想查看文件的磁盤，輸入tree命令，就能夠結構性的查看全部文件。在上述圖中能夠看出文件結構就如同一棵樹，有文件夾，有文件，咱們把文件成爲葉子(Laef)，由於文件不能再展開了，就如樹形結構中葉子是最底層了；把文件夾稱爲容器(Container)，由於文件夾裏既能夠文件夾，又能夠放文件。當想要查看一個磁盤的全部文件時，可使用DFS(深度優先搜索)即遞歸的對每一個文件夾進行一樣的搜索，一條路走到底，當訪問到葉子結點時，再退回去訪問別的結點。this

組合模式結構和實現

Component(抽象構件):它能夠是接口或抽象類，爲葉子構件和容器構件對象聲明接口。定義了訪問管理它的子構件的方法，就是對一個子構件該有的操做都應該在這聲明，如建立子構件，刪除子構件，打開子構件，重命名子構件，複製子構件.......
Leaf(葉子構件):表明一個文件，實如今Component中的行爲，即對文件的操做，能夠是讀文件，寫文件，刪除文件，複製文件......
Composite(容器構件):表明一個文件夾，它提供一個集合放子節點，能夠是文件夾，也能夠是文件，因此它有一個聚合箭頭指向Component，表明能夠遞歸的建立構件

 1 abstract class Component
 2 {
 3     public abstract void Add(Component c);
 4     public abstract void Remove(Component c);
 5     public abstract Component GetChild(int i);
 6     public abstract void Operation();
 7 }
 8 class Leaf : Component
 9 {
10     public override void Add(Component c)
11     {
12         //throw new NotImplementedException();//這裏是報錯，葉子文件沒有此方法的
13     }
14     
15     public override void Remove(Component c)
16     {
17         //throw new NotImplementedException();//同上
18     }
19     
20     public override Component GetChild(int i )
21     {
22         //throw new NotImplementedException();//同上
23         return null;
24     }
25     
26     public override void Operation()
27     {
28         //對文件的可執行方法
29     }    
30 }
31 class Composite : Component
32 {
33     private IList<Component> list = new List<Component>();//這裏通鏈表容器存放文件夾
34     public override void Add(Component c)
35     {
36         list.Add(c);
37     }
38     
39     public override void Remoce(Component c)
40     {
41         list.Remove(c);
42     }
43     
44     public override Component GetChild(int i )
45     {
46         return (Component)list(c);
47     }
48     
49     public override void Operation()
50     {
51         //遞歸實現容器中的對文件的方法
52         foreach(Component child in list)
53         {
54             (Component)child.Operation();
55         }
56     }    
57 }

組合模式的應用

教育機構的OA系統要給各辦公室下發公文(IssuedBytheOfficeDoucument)，採用組合模式模擬實現spa

分析：從圖中能夠看出，北京總部，湖南分校，長沙叫教學點，湘潭教學點這幾個有子構件，因此它們爲文件容器，而教務辦公室，行政辦公室即爲葉子，固然，每一個葉子是不一樣的，要區別開。所以咱們定義一個抽象機構類(AbstractInstitutions)，其中聲明Add，Remove，GetChild和IssuedBytheOfficeDoucument方法。3d

1  abstract class AbstractInstitutions//Component
2     {
3         public abstract void Add(AbstractInstitutions institutions);
4         public abstract void Remove(AbstractInstitutions institutions);
5         public abstract AbstractInstitutions GetChild(int i);
6         public abstract void IssuedBytheOfficeDoucument();
7     }

View Code

教務辦公室，有本身的名字，即哪個教務辦公室，它只能收到下發的公文code

 1  class AcademicAffairsOffice : AbstractInstitutions//Leaf 教務辦公室
 2     {
 3         private string name;
 4         public AcademicAffairsOffice(string name)
 5         {
 6             this.name = name;
 7         }
 8         public override void Add(AbstractInstitutions institutions)
 9         {
10             Console.WriteLine("Can't realize this method!!!");
11         }
12 
13         public override void Remove(AbstractInstitutions institutions)
14         {
15             Console.WriteLine("Can't realize this method!!!");
16         }
17 
18         public override AbstractInstitutions GetChild(int i)
19         {
20             Console.WriteLine("Can't realize this method!!!");
21             return null;
22         }
23 
24         public override void IssuedBytheOfficeDoucument()
25         {
26             Console.WriteLine("issued by the office doucument to the {0}",name);
27         }
28     }

View Code

行政辦公室和教務辦公室相似的實現對象

 1 class AdministrationOffice : AbstractInstitutions//Leaf  行政辦公室
 2     {
 3          private string name;
 4         public AdministrationOffice(string name)
 5         {
 6             this.name = name;
 7         }
 8 
 9         public override void Add(AbstractInstitutions institutions)
10         {
11             Console.WriteLine("Can't realize this method!!!");
12         }
13 
14         public override void Remove(AbstractInstitutions institutions)
15         {
16             Console.WriteLine("Can't realize this method!!!");
17         }
18 
19         public override AbstractInstitutions GetChild(int i)
20         {
21             Console.WriteLine("Can't realize this method!!!");
22             return null;
23         }
24 
25         public override void IssuedBytheOfficeDoucument()
26         {
27             Console.WriteLine("issued by the office doucument to the {0}", name);
28         }
29     }

View Code

容器類中實現抽象構件中的方法，而且要向下屬機構下發公文blog

 1 class TeachArea : AbstractInstitutions//Composite //教學點
 2     {
 3         private string name;
 4         private IList<AbstractInstitutions> AreaList = new List<AbstractInstitutions>();
 5        
 6         public TeachArea(String name)
 7         {
 8             this.name = name;
 9         }
10 
11         public override void Add(AbstractInstitutions institutions)
12         {
13             AreaList.Add(institutions);
14         }
15 
16         public override void Remove(AbstractInstitutions institutions)
17         {
18             AreaList.Remove(institutions);
19         }
20 
21         public override AbstractInstitutions GetChild(int i)
22         {
23             return (AbstractInstitutions)AreaList[i];
24         }
25 
26         public override void IssuedBytheOfficeDoucument()
27         {
28             Console.WriteLine("Issue official documents to the {0}", name);
29             foreach (Object obj in AreaList)
30             {
31                 ((AbstractInstitutions)obj).IssuedBytheOfficeDoucument();
32             }
33         }
34     }

View Code

Program中，要將全部的機構建立出來，並一一Add到對應的容器中，最後有由北京總部向下發送公文繼承

 1 class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             AbstractInstitutions BeijingHeadquarters;
 6             BeijingHeadquarters = new TeachArea("BeijingHeadquarters");
 7 
 8             AbstractInstitutions BeijingAcademicAffairsOffice;
 9             BeijingAcademicAffairsOffice = new AcademicAffairsOffice("BeijingAcademicAffairsOffice");
10             AdministrationOffice BeijingAdministrationOffice;
11             BeijingAdministrationOffice = new AdministrationOffice("BeijingAdministrationOffice");
12 
13             AbstractInstitutions HunanPartition;
14             HunanPartition = new TeachArea("HunanPartition");
15 
16             AbstractInstitutions HunanChangshaArea;
17             HunanChangshaArea = new TeachArea("HunanChangshaArea");
18 
19             AbstractInstitutions HunanXiangtanArea;
20             HunanXiangtanArea = new TeachArea("HunanXiangtanArea");
21 
22             AbstractInstitutions HunanAcademicAffairOffice;
23             HunanAcademicAffairOffice = new AcademicAffairsOffice("HunanAcademicAffairOffice");
24             AbstractInstitutions HunanAdministrationOffice;
25             HunanAdministrationOffice = new AdministrationOffice("HunanAdministrationOffice");
26 
27             Console.WriteLine();
28             AbstractInstitutions ChangshaAcademicAffairOffice;
29             ChangshaAcademicAffairOffice = new AcademicAffairsOffice("ChangshaAcademicAffairOffice");
30 
31             AbstractInstitutions ChangshaAdministrationOffice;
32             ChangshaAdministrationOffice = new AdministrationOffice("ChangshaAdministrationOffice");
33             AbstractInstitutions XiangtanAcademicAffairOffice;
34             XiangtanAcademicAffairOffice = new AcademicAffairsOffice("XiangtanAcademicAffairOffice");
35 
36             AbstractInstitutions XiangtanAdministrationOffice;
37             XiangtanAdministrationOffice = new AdministrationOffice("XiangtanAdministrationOffice");
38 
39             HunanChangshaArea.Add(ChangshaAcademicAffairOffice);
40             HunanChangshaArea.Add(ChangshaAdministrationOffice);
41 
42             HunanXiangtanArea.Add(XiangtanAcademicAffairOffice);
43             HunanXiangtanArea.Add(XiangtanAdministrationOffice);
44 
45             HunanPartition.Add(HunanChangshaArea);
46             HunanPartition.Add(HunanXiangtanArea);
47             HunanPartition.Add(HunanAcademicAffairOffice);
48             HunanPartition.Add(HunanAdministrationOffice);
49 
50             BeijingHeadquarters.Add(BeijingAcademicAffairsOffice);
51             BeijingHeadquarters.Add(BeijingAdministrationOffice);
52             BeijingHeadquarters.Add(HunanPartition);
53             BeijingHeadquarters.IssuedBytheOfficeDoucument();
54         }
55     }

View Code

運行結果：遞歸

透明組合模式和安全組合模式

透明組合模式

在Component中聲明全部的方法，這樣知足了一致性的原則，即對葉子和容器對象都是同樣的處理，不需用再去判斷，這個對象是葉子仍是容器啊，若是是容器，能夠實現哪些方法，若是是葉子，又只能實現哪些方法。這些判斷都不須要。可是，因爲葉子也繼承了Component的方法，所以不安全，葉子對象不能調用Add，Remove，GetChild的方法，若是運行時調用，會出錯，所以要提供錯誤處理代碼(如上述例子中的( Console.WriteLine("Can't realize this method!!!");