Re: blocks and id
Re: blocks and id
On 12 Dec 2012, at 09:57, Andreas Grosam <email@hidden> wrote:
>
> On 12.12.2012, at 10:19, Charles Srstka wrote:
>
>> On Dec 12, 2012, at 3:03 AM, Andreas Grosam <email@hidden> wrote:
>>
>>> How can I check at runtime whether an object (id) is actually a block, and not another kind of object?
>>
>> I don't think there's any good way of doing that right now. You could check the class of the block, but since the block classes are completely undocumented AFAIK, there's no guarantee that the class names won't change in some future release of OS X and break your code.
>>
>> Charles
>>
>
> Thanks for the reply. I feared that.
>
> Currently, I resort to
>
>
> if ([obj isKindOfClass: NSClassFromString(@"NSBlock")])
> …
>
> which evaluates to YES if `obj` is a block. However, NSBlock is not a public class, thus: NSClassFromString(@"NSBlock") which "works" as the time of writing in Mac OS, and returns a class whose name is "NSBlock" (the real block classes are named differently).
>
> I wish there was something official.
>
You could perhaps make this a little less fragile.
typedef void (^MyBlockType)(void);
// we know this is a block
void (^isaBlock)(void) = ^(void) {};
MyBlockType aBlock = ^(void) {NSLog(@"I am a block");};
id qua = aBlock;
if ([qua isKindOfClass:[isaBlock class]]) {
((MyBlockType)qua)();
}
Jonathan
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