Return Obj-C blocks in C++ code

I'm currently porting some classes from the Apple iOS Foundation Framework to C++ and i'm expecting some issues. I'm trying to port this Obj-C method from the NSExpression @class :

- (id, NSArray *, NSMutableDictionary *)expressionBlock

So in my sfExpression class, I have the following code (when deleting others methods ^^)

class sfExpression : public sfObject {
public:
    id (^Expr开发者_运维知识库essionBlock())(id, NSArray*, NSMutableDictionary*);

private:
    NSExpression* _Expression;
};

And when I'm trying to implement this function like this :

id (^sfExpression::ExpressionBlock())(id, NSArray*, NSMutableDictionary*) {
    return [_Expression expressionBlock];
}

It doesn't work... Any ideas ?

I've tried many things but... without success :'(

EDIT : The code is right. Just switch to LLVM Compiler instead of GCC

Edit: Moral of the story, don't use GCC when dealing with blocks.

Here is a full example as far as I can see, this works in my tests.

class Foo
{
public:
    Foo(NSExpression *_exp) : expression([_exp retain])
    {

    }

    ~Foo()
    {
        [expression release];
    }

    id (^ExpressionBlock())(id, NSArray*, NSMutableDictionary*);
private:
    NSExpression *expression;
};

id (^Foo::ExpressionBlock())(id, NSArray*, NSMutableDictionary*)
{
    return [expression expressionBlock];
}


int main()
{
    NSAutoreleasePool *pool = [NSAutoreleasePool new];
    Foo a([NSExpression expressionForBlock:^id(id evaluatedObject, NSArray *expressions, NSMutableDictionary *context) {
        return evaluatedObject;
    } arguments:[NSArray arrayWithObject:@"Test"]]);
    NSLog(@"%@", a.ExpressionBlock()(@"Hello", nil, nil));
    [pool drain];
}

/usr/include/Block.h manipulates ObjC blocks using opaque void pointers, so that's probably what you should use to pass them around to C++ code if you can't compile it with a compiler supporting blocks. Also take note of the Block_copy and Block_release functions in that header. There's also an article on memory management of ObjC blocks.