问题
I just discovered that the Me keyword cannot access private procedures even when they are inside its own class model.
Take the following code in Class1:
Private Sub Message()
Debug.Print "Some private procedure."
End Sub
Public Sub DoSomething()
Me.Message
End Sub
This code instantiates an instance of the class:
Sub TestClass()
Dim objClass As New Class1
objClass.DoSomething
End Sub
Me.Message throws compile error "Method or data member not found."
If I change Private Sub Message() to Public the procedure works fine. I can also remove the Me keyword from the DoSomething procedure, but I was under the impression that the idea behind the Me keyword is to ensure that multiple instances of Class1 are properly encapsulated.
Why can't the VBA Me keyword access procedures in its own module when they are private? Is it safe to omit the Me keyword and do something like this in a class?
Private Sub Message()
Debug.Print "Some private procedure."
End Sub
Public Sub DoSomething()
Message
End Sub
Thanks!
Update: Thanks for the tips on proper syntax, my code is working. I am still looking for an explanation of why Me can reference private procedures in an instance of it's own module. I couldn't find any good documentation.
回答1:
Any guess as to why it was designed that way would be pure supposition without talking to the designers. But my own guess is this, the Me keyword returns a reference to the object the code is currently executing in. I would guess rather than create a special case for Me, they found it easier to continue to obey rules of scope for an object. Which is to say object.method can only work on public or friend methods. So Me, is exactly what it says, an instance of an the currently executing object. And since VBA/VB6 doesn't have shared methods, it doesn't really matter if you prefix with Me or not.
But if it makes you feel any better, I find it incredibly obnoxious too.
回答2:
You do not need the Me keyword to call inside own class.
回答3:
Me is this class object instance. So no one can directly call private subs or functions or access private variables except this class public functions or subs.
回答4:
Public Function Fight() As String
'performs a round of attacks i.e. each character from both sides performs an attack
'returns a scripted version of the outcomes of the round
'check if buccaneers are all dead
If mBuccaneers.aliveCount > 0 Then
'check if any hostiles are alive
If mHostiles.aliveCount > 0 Then
'check we have some buccaneers
If mBuccaneers.count = 0 Then
Fight = "There are no buccaneers. Load or create some buccaneers"
Else
If mHostiles.count = 0 Then
'can't fight
Fight = "There are no hostiles to fight. Generate some hostiles"
Else
mScript = ""
Call GroupAttack(mBuccaneers, mHostiles)
Call GroupAttack(mHostiles, mBuccaneers)
Fight = mScript
End If
End If
Else 'hostiles are all dead
Fight = "Hostiles are all dead. Generate a new set of hostiles"
End If
Else
Fight = "Buccaneers are all dead :(. Suggest building or loading a new buccaneer group"
End If
End Function
Uses the private class method GroupAttack by using the Call statement
Private Sub GroupAttack(attackersGroup As clsGroup, defendersGroup As clsGroup)
'implements the attack of one group on another
Dim victimNo As Integer
Dim randomNumber As Integer
Dim attacker As clsCharacter
Dim damage As Integer
Dim defender As clsCharacter
Randomize
For Each attacker In attackersGroup.members
'check if attacker is still alive
If attacker.health > 0 Then
'check if any defenders are still alive because there's no point attacking dead defenders
If defendersGroup.aliveCount > 0 Then
'do some damage on a defender
If defendersGroup.count > 0 Then
'choose a random hostile
victimNo = Int(((Rnd() * defendersGroup.aliveCount) + 1))
'find an alive victim
memberid = 0
j = 0
Do While j < victimNo
memberid = memberid + 1
If defendersGroup.members(memberid).health > 0 Then
j = j + 1
End If
Loop
'reset our victimno to the live victim
victimNo = memberid
damage = defendersGroup.character(victimNo).attack(attacker.strength)
If damage <> 0 Then 'attacker hit
mScript = mScript & attacker.name & " hits " & _
defendersGroup.character(victimNo).name & " for " & damage & " damage"
If defendersGroup.character(victimNo).health = 0 Then
mScript = mScript & " and kills " & defendersGroup.character(victimNo).name
End If
mScript = mScript & vbCrLf
Else 'attacker missed
mScript = mScript & attacker.name & " missed " & defendersGroup.character(victimNo).name & vbCrLf
End If
End If
End If
End If
Next attacker
End Sub
Thats all you need to do ,works like a charm
回答5:
In COM, there's a difference between the types of object instances and the types of object variables. In particular, the types of object variables behave as interface types. Every type implements at least one interface (itself), but types may implement other interfaces as well. Such ability is used to fake inheritance.
In some frameworks, if class Foo has a private member Bar, then any non-null variable of type Foo will hold a reference to some class object which contains that member. The member may not be accessible to any outside code, but it will exist, and can thus be accessed from anywhere within the code for Foo.
Because COM class-variable types behave like interfaces rather than inheritable class types, however, there's no guarantee that a variable of type Foo will refer to an object which has any of Foo's non-public members. While a compiler could know that Me will always refer to the present object, which will be of actual type Foo, the fact that the only object upon which a private member of Foo could be accessed is Me means that there's no real reason for the compiler to support dot-based dereferencing of private members.
来源：https://stackoverflow.com/questions/1895633/why-cant-the-vba-me-keyword-access-private-procedures-in-its-own-module