主题： Whole-Part关系


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v 1. 对象Whole-Part关系
v 2. 组合／部分关系
v 3. 包含者／内容关系
v 4. 集合／成员关系





1. 对象Whole-Part关系

类别继承(Class inheritance)和对象组合(Object composition)是软件再使用(Reuse)的两大法宝。类别继承就是建立父、子类别之关系例如「学生」可分为「大学生」、「中学生」和「小学生」三类别其继承关系图标如下

图1、 以UML表达类别继承

对象组合的目的是创造「复合对象」(Composite object)例如医院内含医师和护士等其组合关系图标如下


图2、 以UML表达对象组合

继承与组合两大法宝能联合使用以组织庞大的软件系统。例如汽车分为客车、卡车、轿车等子类别而且汽车内含引擎、车体、轮胎等零件则此汽车系统图标如下图3和图4



图3、 汽车的类别继承体系


图4、 汽车的对象组合关系

本节里将进一步分析与说明对象组合方法。尤顿(Yourdon) 认为常见组合关系有三
1) 组合部分(Assembly-parts)关系。
2) 包含内容(Container-contents)关系。
3) 集合成员(Collection-members)关系。





2. 组合／部分关系

组合／部分关系常称为APO(A part of)关系例如汽车是「组合」其内含各零件是「部分」。门是房子的一部分所以房子是「组合」门是「部分」此外窗子也是房子的「部分」。这房子与门窗之关系图标如下


图5、 房子的对象组合关系

以VB表达如下

'ex01.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
'---------------------------------------------------------------------------------
Class House
Class Door
Public size As Double
Public Sub New(ByVal s As Double)
size = s
End Sub
End Class

Class Window
Public size As Double
Public Sub New(ByVal s As Double)
size = s
End Sub
End Class

Private dr As Door
Private win As Window
Public Sub New()
dr = New Door(50)
win = New Window(100)
End Sub
Public Sub Show()
Messagebox.Show("Door: " + str(dr.size) + " Win: " + str(win.size))
End Sub
End Class
'---------------------------------------------------------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form

Public Sub New()
MyBase.New()
Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
......
#End Region
Protected Sub Form1_Click(ByVal sender As Object, ByVal
e As System.EventArgs)
Dim h As New House()
h.Show()
End Sub
End Class

以此程序输出如下
Door: 50 Win: 100


House 之对象诞生后立即诞生内含之Door对象和Window对象。例如宣告指令──
Dim h As New House()

此时h 对象诞生了其内含之dr 和win对象亦诞生了。



此h 通称为「组合对象」(Composite object)而dr 和win 则称为「部分对象」(Component object)。这种关系具有一项特色组合对象与部分对象的寿命应该是一致的。
在逻辑(Logical)意义上，这House 结构中门和窗随着房子而具有「生死与共」之亲蜜关系，也就是寿命一致。在计算机实体(Physical)表达时，House 之对象并不「真正」包含Door及Window之对象只是利用两个参考指向它们。所以上图也可想象如下：


上述两种实体结构皆表达了「组合／部分」关系。请再看个例子：

'ex02.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
'----------------------------------------------------
Class Person
Private p_name As String
Private p_age As Integer

Public Sub New(ByVal na As String, ByVal a As Integer)
p_name = na
p_age = a
End Sub
Public Function isEqual(ByVal obj As Person) As Integer
Dim k As Integer = 0
If Me.p_name = obj.p_name Then
k = 1
End If
isEqual = k
End Function
Public Sub Show()
Messagebox.Show(Me.p_name + ", " + str(Me.p_age))
End Sub
End Class
'---------------------------------------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form

Public Sub New()
MyBase.New()
Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
.........
#End Region
Protected Sub Form1_Click(ByVal sender As Object,
ByVal e As System.EventArgs)
Dim a As New Person("Alvin", 35)
Dim b As New Person("David", 25)
a.Show()
b.Show()
Messagebox.Show(str(a.isEqual(b)))
Messagebox.Show(str(b.isEqual(New Person("David", 32))))
End Sub
End Class

此程序输出
Alvin, 35
David, 25
0
1

「组合」对象之建构者New()程序诞生「部分」对象。此a 、b 两对象之内容为






在isEqual()程序里，两个对象拿其p_name 值来比较。例如a.p_name 值是"Alvin" 而b.p_name 值是"David" 所以a.isEqual(b)表达式之值为0 (False)。







3. 包含者／内容关系

上节的House 结构中门和窗随着房子而具有「生死与共」之亲蜜关系。然而日常生活中常见类似但并不如此亲蜜的情形。例如飞行员坐于飞机驾驶仓内开飞机司机在汽车内驾驶汽车客人乘座于巴士内等等。司机不是汽车的零件客人亦非巴士之组件所以汽车与司机之间并非「组合／部分」关系然而汽车的确包含着司机因之称为「包含者／内容」(Container-contents)关系。
司机和汽车为独立之对象不像引擎一直包含于汽车内于驾驶汽车时司机才被包含于汽车内。显然地司机与汽车之寿命不一样长。「包含者／内容」关系是一种特殊的组合结构其图标方法与「组合／部分」关系相同。例如


此图表达了
◎ 汽车与引擎之间为「组合／部分」关系。
◎ 汽车与司机之间为「包含者／内容」关系。

以VB表达如下

'ex03.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
'----------------------------------------------------
Class Driver
Private name As String
Public Sub New(ByVal na As String)
name = na
End Sub
Public Sub Show()
MessageBox.Show("Driver: " + name)
End Sub
End Class

Class Car
Class Engine
Public model As String
Public Sub New(ByVal mdl As String)
model = mdl
End Sub
End Class

Private e As Engine
Private dr As Driver
Public Sub New()
e = New Engine("Honda")
End Sub
Public Sub assignTo(ByVal d As Driver)
dr = d
End Sub
Public Sub Show()
MessageBox.Show("Engine: " + e.model)
dr.Show()
End Sub
End Class
'----------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form
Public Sub New()
MyBase.New()
Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
.......
#End Region
Protected Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Dim civic As New Car()
Dim d1 As New Driver("Wang")
Dim d2 As New Driver("Kao")
civic.assignTo(d1)
civic.Show()
civic.assignTo(d2)
civic.Show()
End Sub
End Class

此程序输出
Model: Honda
Driver: Wang
Model: Honda
Model" Kao

Car之对象诞生后也诞生Engine之对象e 同时立即指定司机如下指令

Dim civic As New Car()
Dim d1 As New Driver("Wang")
.....
civic.assignTo(d1)
.....

日常生活中的常见情况汽车对象诞生时不须立即指定司机对象。例如汽车出厂时或闲置时并无司机且汽车经常更换司机。此情形下应先诞生civic对象和d1对象，如下：



此时，未立即指定司机而必要时才以assignTo()程序指定司机。例如，将d1指定给civic对象就令civic内之参考变量dr指向d1 对象，如下：



上述程序里，d1、d2及civic 对象之间谁先诞生并无关紧要各独立存在。指令──civic.assignTo(d1) 将d1司机指定给civic 对象另一指令──civic.assignTo(d2)表示改由d2担任civic 之司机。
此Car 类别以参考变量e来指向Engine之对象。现在兹拿上节的Person类别做为例子如果某人(Person 之对象）结婚了就有配偶反之尚未结婚时则无配偶。此时应将Person类别之定义修改如下以表达这种「配偶」关系

'ex04.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
'----------------------------------------------------
Class Person
Private p_name As String
Private p_age As Integer
Private p_spouse As Person

Public Sub New(ByVal na As String, ByVal a As Integer)
p_name = na
p_age = a
End Sub
Public Sub spouse(ByVal sp As Person)
p_spouse = sp
sp.p_spouse = Me
End Sub
Public Sub Show()
Messagebox.Show(Me.p_name + ", " + str(Me.p_age)
+ ", sp: " + Me.p_spouse.p_name)
End Sub
End Class
'----------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form

Public Sub New()
MyBase.New()

Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
......
#End Region
Protected Sub Form1_Click(ByVal sender As Object, ByVal
e As System.EventArgs)
Dim x As New Person("David", 32)
Dim y As New Person("Hellen", 24)
x.spouse(y)
x.Show()
y.Show()
End Sub
End Class

此程序输出
David, 32, sp: Hellen
Hellen, 24, sp: David

资料成员p_spouse指向配偶而配偶亦为Person之对象。所以p_spouse之型态应为Person。一个人刚诞生时并无配偶到结婚时才有配偶所以藉spouce()来建立配偶关系。对象x 与y 结婚之后互为对方之配偶。所以x.p_spouse指向y 而y.p_spouse则指向x 。此时x 和y 之内容如下



于是这Person类别表达了「婚姻」关系。






4. 集合／成员关系

集合意谓着「团体」(Group) 由其成员(Member)组成的群体。例如学校里的社团内有团员公司的销售部含有推销人员。这团体并不像汽车实际包含着司机而只是其成员之集合而已。这情形统称为「集合／成员」(Collection-members)关系。
有趣的是在企业活动中人们规划的方案含许多小方案则大方案是由小方案所组成。例如东北亚旅行团的行程表包括在日本的观光行程、在韩国的观光行程和在香港的观光行程。这总行程表图标如下



总行程是次行程（或称段行程）之集合这是「集合／成员」关系。



此外棒球队是由经理、教练和球员组成订单中含若干产品项目皆为集合／成员关系。实际写程序时不需明确划分「包含者／内容」和「集合／成员」两种关系。其原因是集合与成员之间亦可互为独立不具「生死与共」之亲蜜关系例如「香港观光行程」是独立存在的它既可含于东北亚总行程中又可含于东南亚旅行团的总行程中。因之「集合／成员」关系是一种特殊的「组合」(Composition) 结构。
兹拿上节Person类别做为例子如果Person之对象会加入Club（俱乐部）成为俱乐部的会员则Club与Person之关系为「集合／成员」关系。兹定义Club类别如下

'ex05.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
Imports System.Collections
'----------------------------------------------------
Class Person
Private p_name As String
Private p_age As Integer

Public Sub New(ByVal na As String, ByVal a As Integer)
p_name = na
p_age = a
End Sub
Public Sub display()
Messagebox.Show(Me.p_name + ", " + str(Me.p_age))
End Sub
End Class

Class Club
Private c_name As String
Private pa As ArrayList

Public Sub New(ByVal na As String)
c_name = na
pa = New ArrayList()
End Sub
Public Sub join(ByVal p As Person)
pa.Add(p)
End Sub
Public Sub display()
Messagebox.Show("Club: " + Me.c_name + " has member:")
Dim p As Person
For Each p In pa
p.display()
Next
End Sub
End Class
'-------------------------------------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form

Public Sub New()
MyBase.New()
Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
......
#End Region
Protected Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Dim x As New Club("sogo")
Dim a As New Person("Alvin", 32)
Dim b As New Person("Judy", 28)
x.join(a)
x.join(b)
x.display()
End Sub
End Class


此程序输出
Club: sogo has member:
Alvin, 32
Judy, 28

c_name 指向Strclass之对象这对象内含俱乐部之名称。pa指向ArrayList之对象这对象可包含许多会员(Person)对象。join()程序将Person之对象存入pa所指的ArrayList对象中。
Club之对象含ArrayList之对象此集合对象(Collections)含有Person之对象表达了「集合／成员」关系。例如x 对象内含a 和b 对象。



此图表示"sogo"俱乐部共有"Alvin" 和"Judy"两个会员亦即x 是「集合」而a 和b 是「成员」(Member)。
值得注意这软件是利用已有类别──Strclass及Integer组合成应用类别──Person。再利用Person类别及ArrayList 类别组合成更复杂之应用类别──Club。未来可利用Club及其它类别构筑更大的应用类别依此类推便能创造庞大又可靠的软件了。例如：

'ex06.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
Imports System.Collections
'----------------------------------------------------
Class Person
Private p_name As String
Private p_age As Integer
Public Sub New(ByVal na As String, ByVal a As Integer)
p_name = na
p_age = a
End Sub
Public Sub display()
Messagebox.Show(Me.p_name + ", " + str(Me.p_age))
End Sub
End Class

Class Club
Private c_name As String
Private pa As ArrayList

Public Sub New(ByVal na As String)
c_name = na
pa = New ArrayList()
End Sub
Public Sub join(ByVal p As Person)
pa.Add(p)
End Sub
Public Sub display()
Messagebox.Show("Club: " + Me.c_name + " has member:")
Dim p As Person
For Each p In pa
p.display()
Next
End Sub
End Class
'----------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form

Public Sub New()
MyBase.New()

Form1 = Me
'This call is required by the Win Form Designer.
InitializeComponent()
'TODO: Add any initialization after the InitializeComponent() call
End Sub
'Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
......
#End Region
Protected Sub Form1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
Dim x(2) As Club
x(0) = New Club("sogo")
x(1) = New Club("gold")
Dim a As New Person("Alvin", 32)
Dim b As New Person("Judy", 28)
Dim c As New Person("Bob", 38)
x(0).join(a)
x(0).join(b)
x(1).join(b)
x(1).join(c)
x(0).display()
x(1).display()
End Sub
End Class

此程序输出：

Club: sogo has member:
Alvin, 32
Judy, 28
Club: gold has member:
Judy, 28
Bob, 38

组合对象x 含"sogo"及"gold"两俱乐部其中"gold"俱乐部拥有两个会员──"Alvin" 及"Judy"而"sogo"俱乐部拥有两位会员──"Judy"及"Bob" 。x(0)代表"sogo"俱乐部s(1)代表"gold"俱乐部所以指令── s(0).join( a ) 表示a 加入"gold"俱乐部成为其会员。n

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