[fpc-pascal] 2.1.1 new protected

[Michael Van Canneyt]

On Fri, 11 Aug 2006, Florian Klaempfl wrote:

> Michael Van Canneyt wrote:
>> 
>> 
>> On Fri, 11 Aug 2006, Florian Klaempfl wrote:
>> 
>>> Mattias Gaertner wrote:
>>>> Recently the behaviour of the 'protected' keyword has changed in fpc 
>>>> 2.1.1.
>>>> Now I wonder how can I fix the code, that depends on this.
>>> 
>>> Redesign :)
>>> 
>>>> 
>>>> I have some base classes, that defines methods to let derived classes 
>>>> interact.
>>>> These methods should not be accessed directly from the outside, so they 
>>>> are protected. But this does not work any longer. Of course I can safely 
>>>> typecast, but for aesthetic reasons it looks pretty bad coding style to 
>>>> typecast a class to the wrong class. For example:
>>>> 
>>>> -- unit1 -------------------------
>>>>   TMyClass = class
>>>>     FFlag: boolean;
>>>>   protected
>>>>     procedure InternalSetFlag(b: boolean);
>>>>   end;
>>>> 
>>>> -- unit2 -------------------------
>>>>   TDescendantClass1 = class(TMyClass)
>>>>   public
>>>>     procedure CallProtectedMethod(AnObject: TMyClass);
>>>>   end;
>>>>
>>>>   TDescendantClass2 = class(TMyClass)
>>>>   end;
>>>> 
>>>> procedure TDescendantClass1.CallProtectedMethod(AnObject: TMyClass);
>>>> begin
>>>>   InternalSetFlag(true); // allowed
>>>>   AnObject.InternalSetFlag(true); // not allowed any longer
>>>>   TDescendantClass1(AnObject).InternalSetFlag(true); // allowed and 
>>>> works, but ugly
>>> 
>>> 
>>> Shouldn't be allowed either imo.
>> 
>> Why not ? In a descendent class you 'know' the protected method.
>
> But only of the current instance, no?

Well, nothing is said about this in the manuals; For me this is up to discussion.
It seems normal to me that it is not just the current instance.  You KNOW this 
method is there, in a descendent, so it seems logical that you know that it
exists for another instance as well.

Personally, I think we should allow use of protected methods in a descendent, 
also for other instances. In the above example:
   AnObject.InternalSetFlag(true); 
Should work. But since this is not Delphi compatible, I think this should be
in Objpas mode only.

Michael.