作者: slightboy, 时间: 2006-10-14

首发于: http://cs.alienwave.cn/Topic/329.aspx

看到好多同学权限判断都是用字符串 然后或分割或截取

其实对于 允许/不允许(true/false) 这种的权限, 用逻辑运算再恰当不过了

声明下: 本文针对入门和为掌握的同学, 如果已经懂了那可以无视了

可能意思表达的不是很清楚, 敬请原谅.

逻辑运算符介绍:

And: 逻辑与

1. 0 And 0 = 0
2. 0 And 1 = 0
3. 1 And 0 = 0
4. 1 And 1 = 1

Or: 逻辑或

1. 0 Or 0 = 0
2. 0 Or 1 = 1
3. 1 Or 0 = 1
4. 1 Or 1 = 1

Xor: 异或

1. 0 Xor 0 = 0
2. 0 Xor 1 = 1
3. 1 Xor 0 = 1
4. 1 Xor 1 = 0

Not: 逻辑非

1. Not 1 = 0
2. Not 0 = 1

表达方式介绍:

1 表示 ture, 0 表示 false

举二位为例

第一位 表示 Read 的权限, 第二位 表示 Write 的权限, 可以表示一下四种权限

1. 00 Read(false) Write(false)
2. 01 Read(true) Write(false)
3. 10 Read(false) Write(true)
4. 11 Read(true) Write(true)

运算方式介绍:

还是继续上面的例子

Read = 01(1), Write = 10(2)

1. 00(0) And Read = 0
2. 01(1) And Read = Read
3. 10(2) And Read = 0
4. 11(3) And Read = Read

1. 00(0) And Write = 0
2. 01(1) And Write = 0
3. 10(2) And Write = Write
4. 11(3) And Write = Write

下面给出示例代码:

权限定义类(要有枚举类型该多好啊...)

Class PermissionType
Public Read
Public Write
Public Delete
Private Sub Class_Initialize
Read = 1
Write = 2
Delete = 4
End Sub
End Class

权限类

Class PermissionSetComponent
Private intValue
Public Property Get Read()
Read = GetValue(Permission.Read)
End Property
Public Property Let Read(arg)
Call SetValue(Permission.Read, arg)
End Property
Public Property Get Write()
Write = GetValue(Permission.Write)
End Property
Public Property Let Write(arg)
Call SetValue(Permission.Write, arg)
End Property
Public Property Get Delete()
Delete = GetValue(Permission.Delete)
End Property
Public Property Let Delete(arg)
Call SetValue(Permission.Delete, arg)
End Property
Public Property Get Value()
Value = intValue
End Property
Public Property Let Value(arg)
intValue = arg
End Property
Public Function GetValue(intType)
GetValue = (Value and intType) = intType
End Function
Public Sub SetValue(intType, boolValue)
IF (boolValue) Then
Value = Value Or intType
Else
Value =  Value And (Not intType)
End IF
End Sub
End Class

运用示例代码:

Dim Permission : Set Permission = new PermissionType
Dim PermissionSet : Set PermissionSet = new PermissionSetComponent
PermissionSet.Value = 0
w("Read:")
PermissionSet.Read = false
w(PermissionSet.Value &" "& PermissionSet.Read)
PermissionSet.Read = true
w(PermissionSet.Value &" "& PermissionSet.Read)
w("Write:")
PermissionSet.Write = false
w(PermissionSet.Value &" "& PermissionSet.Write)
PermissionSet.Write = true
w(PermissionSet.Value &" "& PermissionSet.Write)
w("Delete:")
PermissionSet.Delete = false
w(PermissionSet.Value &" "& PermissionSet.Delete)
PermissionSet.Delete = true
w(PermissionSet.Value &" "& PermissionSet.Delete)
Function w(o)
Response.Write("<br />"& o)
End Function

今天的课程就到这里, 大家可以举一反三, 下课...