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Ed Evans
Guest
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 Posted: Tue Jun 22, 2004 10:51 pm Post subject: Strange EInvalidTypecast exceptions |
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I've got an odd situation that raises a typecast exception.
I have a couple types in a pas file:
TFooBase = class
// blah
end;
TFoo = class(TFooBase)
// more blah
end;
This pas file is seperately compiled into a package and an exe
project. The package has a method like:
function MakeFoo(): TFooBase;
begin
result := TFooBase.Create();
end;
When the exe runs, it loads the package via LoadPackage, and
eventually calls MakeFoo like this:
procedure someproc();
var
fooBase: TFooBase;
begin
fooBase := MakeFoo();
Assert( fooBase.ClassName = 'TFoo' ); // This works
Assert( foo is TFoo ); // This fails
end;
Any ideas?
Cheers,
Ed Evans
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Zakath
Guest
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| Posted: Wed Jun 23, 2004 9:51 pm Post subject: Re: Strange EInvalidTypecast exceptions |
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Ed Evans wrote:
| Quote: | I've got an odd situation that raises a typecast exception.
I have a couple types in a pas file:
TFooBase = class
// blah
end;
TFoo = class(TFooBase)
// more blah
end;
This pas file is seperately compiled into a package and an exe
project. The package has a method like:
function MakeFoo(): TFooBase;
begin
result := TFooBase.Create();
end;
When the exe runs, it loads the package via LoadPackage, and
eventually calls MakeFoo like this:
procedure someproc();
var
fooBase: TFooBase;
begin
fooBase := MakeFoo();
Assert( fooBase.ClassName = 'TFoo' ); // This works
Assert( foo is TFoo ); // This fails
end;
Any ideas?
//If you add a new |
type
TFooClass = class of TFooBase;
//And then modify MakeFoo
function MakeFoo(FC: TFooClass): TFooBase;
begin
result := FC.Create();
end;
//You can then test it with (works for me)
var
fooBase: TFooBase;
begin
fooBase := MakeFoo(TFoo);
Assert(fooBase.ClassName = 'TFoo');
Assert(fooBase is TFoo);
fooBase.Free;
end.
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