[fpc-pascal] Interface performance

[Andrew Haines]

On 11/11/2016 10:14 PM, Ryan Joseph wrote:
> Arr := TArray.Create;
> Obj := ObjInt.GetObject;
> Arr.AddObject(Obj);
>
> [do some stuff]
>
> // here the problems start because TArray always returns TObject
> // and I can’t cast TObject to IMyInterface even though the object
> // stored in the array does in fact implement IMyInterface
>
> ObjInt := IMyInterface(Arr.GetObject(0)); // error! but I need to get a reference to IMyInterface from the array
>
> // I have to use “as” or Supports here and it defeats the purpose
> ObjInt := Arr.GetObject(0) as IMyInterface;

  You have two options if you have a list of TObject.

1.  (Arr.GetObject(n) as IMyInterface).DoSomething;

2.  TMyObjectClass(Arr.GetObject(n)).DoSomething;

2 is kind of pointless because the interface is not being used so why 
have it.

Probably it is better to keep a list of IMyInterface rather than TObject.


I made a small test and uploaded it to github if you want to check it 
out. It uses a list of IMyInterface.

https://github.com/andrewd207/interfacetest

Or as a zip:

https://github.com/andrewd207/interfacetest/archive/master.zip


Regards,

Andrew Haines