[fpc-devel] "class of TFoo".Create

[J. Gareth Moreton]

What I mean is that if you want to instantiate an object of class TFoo, 
you'd call TFoo.Create, not TFooClass.Create.

If you want to take advantage of Object Pascal's unique polymorphism and 
instantiate a descendant class of TFoo, you'd call 
MetaClassVariable.Create rather than TFooClass.Create, where 
MetaClassVariable is defined somewhere as "var MetaClassVariable: 
TFooClass;" and then set it accordingly before the instantiation.

To just call TFooClass.Create, and TFooClass is implicitly converted to 
TFoo, feels a bit 'off' and is asking for trouble, while seeing 
"TFooClass.Create" in the code would be indictive of a bug in my 
opinion, since the programmer either meant "TFoo" or a variable of type 
TFooClass instead of "TFooClass" itself.

On 06/07/2025 15:17, Zoë Peterson via fpc-devel wrote:
>> I would personally call that unusual at best
>
> What do you two expect this construct to do that you think the current behavior is wrong? It’sobviously correct and expected to me as a fundamental  part of Object Pascal’s polymorphism. Constructing an object from a class reference is the entire reason that constructors are virtual. It’s how things like TPicture.Graphic are implemented to create the correct image loading object.
>
> Zoë Peterson
> Scooter Software
>
>
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