[fpc-pascal] How to use a static method as procedure variable?

silvioprog silvioprog at gmail.com
Sun Jul 12 00:11:02 CEST 2015


On Sun, Jul 5, 2015 at 2:41 PM, Ewald <ewald at yellowcouch.org> wrote:

>
> On 30 Jun 2015, at 20:54, silvioprog wrote:
>
>
> The code above compiles fine in Delphi (tested in XE 7), but in FPC I got
> the following compiling error:
>
> Unit1.pas(46,14) Error: Incompatible types: got "<class method type of
> procedure({Open} Array Of Byte;out AnsiString) of object;Register>"
> expected "<procedure variable type of procedure({Open} Array Of Byte;out
> AnsiString);Register>".
>
> Is this a bug or I need to enable some switch?
>
>
> Back in 2012 I had a similar issue. Original message can be found here:
> http://lists.freepascal.org/pipermail/fpc-pascal/2012-December/035921.html
>
> I fixed it by declaring a type that includes the hidden parameter
> mentioned in that thread, so in your case:
>
>     Type
> TMyProc = procedure(aClassType: TClass; ABytes: array of Byte; out
> AOutput: AnsiString);
>
> the invocation then becomes
> FMyProc(ClassType, [65, 66, 67], S);
>
> instead of
> FMyProc([65, 66, 67], S);
>
> And, of course, the assignment to FMyProc becomes more verbose and less
> type-safe:
> FMyProc := TMyProc(Pointer(@DoMyProc));
>
> NOTE: This is a hack. It is not documented anywhere, but i have used this
> approach since late 2012 without any problems so far. Better be careful and
> write a small sanity test that checks correct operation every time you use
> a new compiler.
>

Very nice, I'll try that, thank you! =)

-- 
Silvio Cl├ęcio
My public projects - github.com/silvioprog
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