系统设计中的业务验证设计1

要求业务验证的情况大致可以分为3类

1、某一个值本身需要验证

2、仅当另外一个值出现时,某一个值需要验证

3、仅当另外一个数据集里面包含的某一个数据满足某个条件时,某一个值需要验证

业务逻辑的验证要求验证方法集中处理,尽量避免在整个系统中对同一个值存在多个业务验证。

验证:返回true或false的方法,该方法必须包含两个参数,1、验证数据本身;2、验证数据的处理方法

验证中必须理解的技术:

delegate:表示委托,委托是一种数据结构,它引用静态方法或引用类实例及该类的实例方法。要求被引用方法的参数和返回值和delegate声明的方法一致的类。该类的方法就可以被delegate类型调用。

一下为两个例子:

例子一:

Public Class SamplesDelegate

' 为一个方法申明委托
Delegate Function myMethodDelegate(myInt As Integer) As [String]

' 申明委托能够指向的方法
Public Class mySampleClass

' 定义需要实例化的方法.
Public Function myStringMethod(myInt As Integer) As [String]
If myInt > 0 Then
Return "positive"
End If
If myInt < 0 Then
Return "negative"
End If
Return "zero"
End Function 'myStringMethod

' 定义静态方法
Public Shared Function mySignMethod(myInt As Integer) As [String]
If myInt > 0 Then
Return "+"
End If
If myInt < 0 Then
Return "-"
End If
Return ""
End Function 'mySignMethod
End Class 'mySampleClass

Public Shared Sub Main()

' 为每个方法申明一个委托myD1,myD2.
Dim mySC As New mySampleClass()
Dim myD1 As New myMethodDelegate(AddressOf mySC.myStringMethod)'引用实例方法
Dim myD2 As New myMethodDelegate(AddressOf mySampleClass.mySignMethod)'引用静态方法

' 通过委托调用.
Console.WriteLine("{0} is {1}; use the sign ""{2}"".", 5, myD1(5), myD2(5))
Console.WriteLine("{0} is {1}; use the sign ""{2}"".", - 3, myD1(- 3), myD2(- 3))
Console.WriteLine("{0} is {1}; use the sign ""{2}"".", 0, myD1(0), myD2(0))

End Sub 'Main

End Class 'SamplesDelegate

例子二:

Public Class SortClass


   '声明委托
   **Delegate** Function Compare(ByVal x As Integer, _
                                 ByVal y As Integer) As Boolean

   '申明委托指向的实例方法  
   Function CompareValues(ByVal X As Integer, _
                          ByVal Y As Integer) As Boolean
      If X &gt; Y Then
         CompareValues = True
      Else
         CompareValues = False
      End If
   End Function

   '声明使用委托的方法  
   Sub SelectionSort(ByVal IsGreaterThan As **Compare** , _
                     ByVal IntArray() As Integer)
      Dim MaxVal As Integer
      Dim MaxIndex As Integer
      Dim i, j As Integer

      ' Step through the elements in the array starting with the
      ' last element in the array.
      For i = UBound(IntArray) To 1 Step -1
         MaxVal = IntArray(i)
         MaxIndex = i
         For j = 1 To i
            ' 使用委托.
            If **IsGreaterThan**.Invoke(IntArray(j), MaxVal) Then
               MaxVal = IntArray(j)
               MaxIndex = j
            End If
         Next j
         ' 使用委托.
         If **IsGreaterThan**.Invoke(i, MaxIndex) Then
            IntArray(MaxIndex) = IntArray(i)
            IntArray(i) = MaxVal
         End If
      Next i
   End Sub
End Class

Class Class1
   Sub SortArray()  
      '声明被委托指向的实例化对象
      Dim **Sort** As New SortClass()
      Dim arr1() As Integer = {1, 5, 3, 2, 7, 22, 5, 54, 12}
      Sort.SelectionSort(AddressOf **Sort**.CompareValues, arr1)
      MsgBox("Array sorted.")
   End Sub
End Class

   '测试   
   Private Sub Button1_Click(ByVal sender As System.Object, _
                             ByVal e As System.EventArgs) _
                             Handles Button1.Click
      Dim c As New Class1()
      c.SortArray()
   End Sub
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