2011/11/5 Michael Van Canneyt <mich...@freepascal.org>:
> Procedure SomeOuter;
>
> Var
> d,e,f : SomeType;
>
> Procedure
> SomeInner(targetobject:ttargetobject;a:integer;b:someobject;c:string)
> begin
> targetobject.destinationprocedure(a,b,c);
> end;
>
> begin
> Targethread.queue(@SomeInner(aobject,d,e,f));
> end;
>
> No difference with 'closure', except more readable.
>
> Michael.
I doubt that this would even compile. Also As I pointed out already
the example was wrong, the procedure does not have any arguments, the
closure must be "closed over" these variables.
and this:
begin
Targethread.queue(@SomeInner);
end;
would compile but it would just pass the procedure variable. This is
not a closure. How is the other thread supposed to know the values of
the variables that existed only in the scope of SomeOuter?
A closure would be something like this:
Procedure SomeOuter;
Var
d,e,f : SomeType;
Procedure SomeInner
begin
targetobject.destinationprocedure(a,b,c);
end;
begin
Targethread.queue(SomeInner);
end;
The compiler would need to create an object on the heap containing the
procedure *along* with the needed variables a,b,c and then pass the
entire object. The receiving side could then call this method and it
would still have access to these variables.
A closure has enclosed variables from the surrounding scope where it
was created, hence the name 'closure'. You cannot do this with a
procedure variable alone, you need an object on the heap to contain
the enclosed variables. The Delphi compiler will behind the scenes
create a reference counted object with an 'invoke' method (the
procedure SomeInner) and all its needed variables.
It is basically a syntactic shortcut to explicitly defining this
class, and creating an instance of it.
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