从简单工厂模式看MVC

上次米老师把我叫过去，问了一通MVC的东西，在确定我真的是不知道之后，决定让李坤师哥给我们来不上这么一课——很重要的一课——对于UML以及应用。

想了几天关于mvc的东东，再加上上次米老师给我说的，我现在用一个例子来说明一下。就是简单工厂模式——这也是米老师当时给我讲的。

类的关系图是这样的：

从这个图中应该很容易看得出其中各个模块之间的关系，对比一下M-V-C图：

 

其中SimpleFactory就是控制器，通过这个工厂来控制视图和模型之间的关系。

下面给出模型模块：

在这个模块中实现了具体细节方面的数据的技术以及返回。

 

Public MustInherit Class Calc Protected _NumberA As Double Protected _NumberB As Double Protected _result As Double Public MustOverride Property NumberA() Public MustOverride Property NumberB() Public MustOverride Property Result() Public MustOverride Function GetResult() As DoubleEnd ClassPublic Class Add : Inherits Calc Public Overrides Function GetResult() As Double Result = NumberA + NumberB Return Result End Function Public Overrides Property Result() As Object Get Return _result End Get Set(ByVal value As Object) _result = value End Set End Property Public Overrides Property NumberA() As Object Get Return _NumberA End Get Set(ByVal value As Object) _NumberA = value End Set End Property Public Overrides Property NumberB() As Object Get Return _NumberB End Get Set(ByVal value As Object) _NumberB = value End Set End PropertyEnd ClassPublic Class mSub : Inherits Calc Public Overrides Function GetResult() As Double Result = NumberA - NumberB Return Result End Function Public Overrides Property Result() As Object Get Return _result End Get Set(ByVal value As Object) _result = value End Set End Property Public Overrides Property NumberA() As Object Get Return _NumberA End Get Set(ByVal value As Object) _NumberA = value End Set End Property Public Overrides Property NumberB() As Object Get Return _NumberB End Get Set(ByVal value As Object) _NumberB = value End Set End PropertyEnd ClassPublic Class Mul : Inherits Calc Public Overrides Function GetResult() As Double Result = NumberA * NumberB Return Result End Function Public Overrides Property Result() As Object Get Return _result End Get Set(ByVal value As Object) _result = value End Set End Property Public Overrides Property NumberA() As Object Get Return _NumberA End Get Set(ByVal value As Object) _NumberA = value End Set End Property Public Overrides Property NumberB() As Object Get Return _NumberB End Get Set(ByVal value As Object) _NumberB = value End Set End PropertyEnd ClassPublic Class Div : Inherits Calc Public Overrides Function GetResult() As Double Result = NumberA / NumberB Return Result End Function Public Overrides Property Result() As Object Get Return _result End Get Set(ByVal value As Object) '防止除数为0. Try _result = value Catch ex As Exception MsgBox(ex.Message) End Try End Set End Property Public Overrides Property NumberA() As Object Get Return _NumberA End Get Set(ByVal value As Object) _NumberA = value End Set End Property Public Overrides Property NumberB() As Object Get Return _NumberB End Get Set(ByVal value As Object) _NumberB = value End Set End PropertyEnd Class 

 

然后再来看控制器模块：

这个模块将从视图中传递过来的事件，控制分配到相应的类中。

Public Class SimpleFactory Public Shared Function createOperate(ByVal operate As String) As Calc Dim oper As Object Select Case operate Case "+" oper = New Add Case "-" oper = New mSub Case "*" oper = New Mul Case "/" oper = New Div Case Else oper = Nothing End Select Return oper End FunctionEnd Class

最后来看视图：

Public Class ViewFrm Private Sub BtnRun_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnRun.Click Dim oper As Calc oper = SimpleFactory.createOperate(cmb.Text) oper.NumberA = CDbl(txtNumA.Text) oper.NumberB = CDbl(txtNumB.Text) lblResult.Text = CStr(oper.GetResult()) End SubEnd Class

不知道我的理解正不正确，从视图中看，首先是定义了一个Calc类，然后通过简单工厂来实例化这个类，也就是通过控制器进行相应的调配，最后调配完之后，即可直接使用返回的具体类来进行操作。

这个例子中的视图，控制器，模型，都是相互独立的。你比如说我要用控制台来进行计算，那就直接改变视图类就可以了。至于说到对控制器的改动以及对模型的改动。在这个例子中不太能体现出来。