New to inheritance, simple question

[Edwin Knoppert]

This seems to work fine:

Class Class1

    Interface Class1_Interface1: Inherit IUnknown

        Method TEST() As String
            Method = "1234"
        End Method

    End Interface

End Class

Class Class2

    Interface Class2_Interface1: Inherit Class1, Class1_Interface1

        Override Method TEST() As String
            Method = "2345"
        End Method

    End Interface

End Class

Function Test() As Long

    Local i1 As Class1_Interface1
    Local i2 As Class2_Interface1
    
    i1 = Class "Class1"
    i2 = Class "Class2"    

    MsgBox i1.TEST() & ", " & i2.TEST()

End Function

Question is that i have a single variable of a specific interface type where i want to refer to the class created.
Like:

Function Test() As Long

    Local i2 As Class2_Interface1
    Local i As Class1_Interface1
    
    i2 = Class "Class2"    
    i = i2

    MsgBox i.TEST()

End Function

So that i get's independent from the actual type.
In practice i would like to do this:

Function Test() As Long

    Local i As Class1_Interface1
    i = Class "Class2"    
    MsgBox i.TEST()

End Function

The above fails but is my logic flawed?
If not should store the interface in an IUnknown type?
IUnknown is afaik not mentioned in the help to be a variable type.

[José Roca]

    Local i As Class1_Interface1
    i = Class "Class2"

The above fails but is my logic flawed?

Yes. There is not a Class1_Interface1 in Class2. This is COM, not C++, Java or wathever.

Either use:

    Local i As Class1_Interface1
    i = Class "Class1"

or:

    Local i As Class2_Interface1
    i = Class "Class2"

If not should store the interface in an IUnknown type?
IUnknown is afaik not mentioned in the help to be a variable type.

It is not a variable type. It is an interface name.

[Edwin Knoppert]

The point is that i need to hold a reference to these kind of interfaces in a single variable so i can call them using the same variable name and functionset while internally the interfaces handle their code differently..

Iow ordinary inheritance stuff but what var type shall use to be able to hold any of the interfaces described?

[Brian Chirgwin]

non random GUIDs?

The point is that i need to hold a reference to these kind of interfaces in a single variable so i can call them using the same variable name and functionset while internally the interfaces handle their code differently..

Iow ordinary inheritance stuff but what var type shall use to be able to hold any of the interfaces described?

Great question, I was just working on this. I have a partial answer, but not sure if I am correct.

The following code works, but am I asking for trouble. If this is correct, it seems PB should automatically assign the same GUID (not random) in when using an inherit class, interface.

Can anyone confirm that this a valid approach or is this asking for trouble (assigning the same GUID to different interfaces)?

#Compile Exe
#Dim All

' Note: These guids taken from help file and not gauranteed to be unique
' for demo purposes only

$cPerson = Guid$("{00000099-0000-0000-0000-000000000008}")
$iPerson = Guid$("{00000099-0000-0000-0000-000000000009}")
$cEmployee = Guid$("{00000099-0000-0000-0000-000000000010}")
$iEmployee = Guid$("{00000099-0000-0000-0000-000000000009}") ' NOTE same as iPerson

Class cPerson $cPerson
    Instance sLastName As String
    Instance sFirstName As String
    Instance sAddress As String
    Instance sCity As String
    Instance sState As String
    Instance sZip As String

    Interface iPerson $iPerson
        Inherit IUnknown

        Property Get Lastname () As String
            Property = sLastname
        End Property

        Property Set Lastname(ByVal lName As String)
            sLastname = lname
        End Property

        Property Get Firstname() As String
            Property = sFirstName
        End Property

        Property Set firstName(ByVal fName As String)
            sFirstname = fname
        End Property

        Property Get Address() As String
            Property = sAddress
        End Property

        Property Set Address(ByVal sAddr As String)
            sAddress = sAddr
        End Property

        Property Get City() As String
            Property = sCity
        End Property

        Property Set City (ByVal sNewCity As String)
            sCity = sNewCity
        End Property

        Property Get State() As String
            Property = sState
        End Property

        Property Set State(ByVal sNewState As String)
            sState = sNewState
        End Property

        Property Get Zip() As String
            Property = sZip
        End Property

        Property Set Zip(ByVal sNewZip As String)
            sZip = sNewZip
        End Property

        Method FullName() As String
            Method = sFirstname + " " + sLastname
        End Method

        Method LastNameCommaFirst() As String
            Method = sLastname + ", " + sFirstname
        End Method

        Method AddressLabel() As String
            Method = me.FullName + $CrLf + me.Address + $CrLf + me.City + ", " + me.State + " " + me.Zip
        End Method

    End Interface

End Class

Class cEmployee $cEmployee
    Instance sTitle As String
    Instance sSalary As String

    Interface iEmployee $iEmployee
        Inherit cPerson, iPerson

        Override Method AddressLabel() As String
            Method = Me.Title + " " + me.FullName + $CrLf + me.Address + $CrLf + me.City + ", " + me.State + " " + me.Zip
        End Method

        Property Get Title () As String
            Property = sTitle
        End Property

        Property Set Title (ByVal newTitle As String)
            sTitle = newTitle
        End Property

    End Interface

End Class

Function printAddress (obj As iPerson) As String
    Function = obj.addresslabel
End Function

Function PBMain () As Long

    Dim persons(10) As iPerson

    Local i As Long
    Local person As iPerson

    Local person2 As iEmployee

    For i = 0 To 10
        If i Mod 2 = 0 Then

            person = Class "cPerson"
            person.firstname = "John"
            person.lastname = "Smith"
            person.address = "123 Main Street"
            person.city = "Anytown"
            person.state = "Anywhere"
            person.zip = "12345"

            persons(i) = person

        Else
            person2 = Class "cEmployee"
            person2.Title = "President"
            person2.firstname = "Jane"
            person2.lastname = "Doe"
            person2.address = "123 Main Street"
            person2.city = "Anytown"
            person2.state = "Anywhere"
            person2.zip = "12345"
            persons(i) = person2
        End If
    Next i

    For i = 0 To 10
        MsgBox printaddress(persons(i))
    Next i


'    MsgBox person.FullName & $CrLf & person2.fullname
'    MsgBox person.LastnameCommaFirst & $CrLf & person2.LastnameCommaFirst
'    MsgBox person.addresslabel

End Function

[Edwin Knoppert]

While it works, i would like to avoid this kind of code:

Class Class1

    Class Method Destroy
        MsgBox "Destroy Class1"
    End Method

    Interface Class1_Interface1: Inherit IUnknown

        Method TEST() As String
            Method = "1234"
        End Method

    End Interface

End Class

Class Class2

    Class Method Destroy
        MsgBox "Destroy Class2"
    End Method

    Interface Class2_Interface1: Inherit Class1, Class1_Interface1

        Override Method TEST() As String
            Method = "2345"
        End Method

    End Interface

End Class

Function Test() As Long

    Local i1 As Class1_Interface1
    Local i2 As Class2_Interface1
    
    i2 = Class "Class2"    
    [B]Poke Dword, VarPtr( i1 ), ObjPtr( i2 )
    i1.addref()[/B]

    MsgBox i1.TEST() & ", " & i2.TEST()

End Function

[jcfuller]

Edwin,
That's the only way I know to do it.

James

[Edwin Knoppert]

That's not so nice, fortunately i just discovered PB checks the sequence of it's methods so it maybe suitable to move the pointer to another typedef.

Here is a better example what i need:

[color=#0000FF]Class[/color] clsImportObject

    [color=#0000FF]Interface[/color] iImportObject: [color=#0000FF]Inherit[/color] [color=#0000FF]IUnknown[/color]
    
        [color=#0000FF]Method[/color] GetImportName() [color=#0000FF]As[/color] [color=#0000FF]String[/color]
            [color=#0000FF]Method[/color] = "Unknown"
        [color=#0000FF]End[/color] [color=#0000FF]Method[/color]

    [color=#0000FF]End[/color] [color=#0000FF]Interface[/color]

[color=#0000FF]End[/color] [color=#0000FF]Class[/color]

[color=#0000FF]Class[/color] clsUNIT4AGRESSO

    [color=#0000FF]Interface[/color] UNIT4AGRESSO_iImportObject: [color=#0000FF]Inherit[/color] clsImportObject, iImportObject
    
        Override [color=#0000FF]Method[/color] GetImportName() [color=#0000FF]As[/color] [color=#0000FF]String[/color]
            [color=#0000FF]Method[/color] = "UNIT4AGRESSO"
        [color=#0000FF]End[/color] [color=#0000FF]Method[/color]    

    [color=#0000FF]End[/color] [color=#0000FF]Interface[/color]

[color=#0000FF]End[/color] [color=#0000FF]Class[/color]

[color=#0000FF]Macro[/color] Import_CreateObject(p1, p2)
    [color=#0000FF]MacroTemp[/color] i2
    [color=#0000FF]Dim[/color] i2 [color=#0000FF]As[/color] p2
    i2 = [color=#0000FF]Class[/color] p1
    i = [color=#0000FF]Nothing[/color]
    [color=#0000FF]If[/color] [color=#0000FF]IsObject[/color]( i2 ) [color=#0000FF]Then[/color]
        [color=#0000FF]Poke[/color] [color=#0000FF]Dword[/color], [color=#0000FF]VarPtr[/color]( i ), [color=#0000FF]ObjPtr[/color]( i2 )
        i.Addref()
        i2 = [color=#0000FF]Nothing[/color]
    [color=#0000FF]End[/color] [color=#0000FF]If[/color]
[color=#0000FF]End[/color] [color=#0000FF]Macro[/color]

[color=#0000FF]Function[/color] Test( [color=#0000FF]ByVal[/color] nIndex [color=#0000FF]As[/color] [color=#0000FF]Long[/color] ) [color=#0000FF]As[/color] [color=#0000FF]Long[/color]

    [color=#0000FF]Local[/color] i [color=#0000FF]As[/color] iImportObject

    [color=#0000FF]Select[/color] [color=#0000FF]Case[/color] nIndex
    [color=#0000FF]Case[/color] 0: i = [color=#0000FF]Class[/color] "clsImportObject"    
    [color=#0000FF]Case[/color] 1: Import_CreateObject( "clsUNIT4AGRESSO", UNIT4AGRESSO_iImportObject )
    [color=#0000FF]Case[/color] [color=#0000FF]Else[/color]
        [color=#0000FF]Exit[/color] [color=#0000FF]Function[/color]
    [color=#0000FF]End[/color] [color=#0000FF]Select[/color]

    [color=#0000FF]If[/color] [color=#0000FF]IsNothing[/color]( i ) [color=#0000FF]Then[/color] [color=#0000FF]Exit[/color] [color=#0000FF]Function[/color]

    [color=#0000FF]MsgBox[/color] i.GetImportName()
    
    [color=#007F00]' More i... calls here....[/color]

[color=#0000FF]End[/color] [color=#0000FF]Function[/color]

[Edwin Knoppert]

Same problems arrise if you try to return a different interface like:

        Property Get SQL() As ImportObject_ISQL
            Property = Me
        End Property

And:

        Override Property Get SQL() As UNIT4AGRESSO_ISQL
            Property = Me
        End Property

Hmm, rather complex at this time for me.
I know doable but so far not with strong typed coding techniques i guess.