[Gambas-user] Gambas 3 advancement

[Benoît Minisini]

> 2010/12/19 Benoît Minisini <gambas at ...1...>:
> > Tell me the important things I forgot, because I am sure I have forgotten
> > things.
> > 
> > Not the small bugs, but the features that may change the language syntax
> > or the interface of some components.
> 
> Hi Benoît. I think that a "mecanism" for automatic and selective
> sharing of public methods, properties and events from objects that are
> members of another, to it's container object, will be useful.
> 
> Example. The ValueBox is compound for a TextBox, but the interface of
> TextBox isn't shared with ValueBox, nothing at all. If I want to share
> the complete interface of TextBox with ValueBox I should use
> inheritance, but there's no an automatic way to share partially and
> automatically the interface of TextBox to ValueBox because TextBox is
> a member of ValueBox (composition). So, this should be done manually,
> repeating the mayor part of interface of TextBox in ValueBox (there's
> no big deal in this case, but in others could be).
> 
> Note: when a control is based on Control or UserControl through
> inheritance, some properties inherited (maybe methods too) have no
> sense in the new control, but inheritance have no way to anulate some
> members in the subclass, is all or nothing. In similar way composition
> or association forces to make public the member that "is part" or "is
> used", allowing access to it's complete interface (and, again, this
> many times haven't sense) or make it private, preventing access
> absolutely. (Containers are a special case that breaks the
> encapsulation through the collection "Children"). An new mecanism for
> selectively share part of interface of the an object for
> 
> May be would be useful can do something like that:
> 
> ' Inside ValueBox class
> shareInterface(TextBox, ValueBox, noneExcept, Name, X, Y, W, H, ...,
> Click, KeyPress, ... , Refresh, Resize, ...)
> 
> shareInterface(TextBox, ValueBox, allExcept, Text, Password, ... )
> 
> 'Syntax
> shareInterface(FromClass, ToClass, { allExcept | noneExcept } ,
> [properties] [events] [methods] )
> 
> 
> A name conceptually more accurate could be "Delegate"
> 
> 'Syntax
> Delegate(ToClass, FromClass, { allExcept | noneExcept } , [properties]
> [events] [methods] )
> 
> 
> 
> Good or crazy idea?

You can't "remove" something in inheritance, because if B inherits A, then B 
is an A. So if the method m() (or a property) applies to A, it must applies to 
B too.

Having to reimplement the interface in the composition case does not shock me. 
If you really want inheritance, use inheritance.

But I admit it's a boring thing to write. Maybe a delegation mechanism could 
be implemented, but not in Gambas 3 I think.

Note: delegation needs an object. For example, ValueBox will use its inner 
TextBox as a delegate.

I'm currently implementing a Proxy class that allows to automatically delegate 
events from one object to another one. But the result is not beautiful. I must 
think about all that...

-- 
Benoît Minisini