Typecasting from open array parameter to TArray<>

Question

Check the following code:

function A(const points: TArray<TPoint>): Boolean;
begin
   //Something
end;

procedure B(var pts: array of TPoint)
begin
   A(pts); //Compiler error E2010 Incompatible types
end;

It yields a compiler error:

E2010 Incompatible types: 'System.TArray' and 'array of TPoint'

Calling A(TArray<>(pts)); doesn't work. I solve the problem doing

A(TArray<TPoint>(@pts));

Is it the proper way to typecast an open array parameter to TArray<>? Is there any other way?

Please assume that parameters type of both function can not be changed.

Possible duplicate of Why casting an open array parameter to an array type causes E2089 Invalid typecast? — Remy Lebeau
– Remy Lebeau, Commented May 29, 2018 at 19:37

David Heffernan · Accepted Answer · 2018-05-29 13:26:58Z

3

You cannot perform such a typecast. An open array is no a dynamic array. Your options include:

Use a dynamic array for both procedures.
Use an open array for both procedures.
Copy the content of the open array to a dynamic array, and pass that.

Of these I would note that copying is expensive and I would reject that option on principle.

answered May 29, 2018 at 13:26

David Heffernan

616k46 gold badges1.1k silver badges1.5k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

David Heffernan Over a year ago

It just looks like it works. But there are some actions that will fail.

Collectives™ on Stack Overflow

Typecasting from open array parameter to TArray<>

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related