On 12 Dec 2012, at 09:57, Andreas Grosam <agro...@onlinehome.de> wrote:
>
> On 12.12.2012, at 10:19, Charles Srstka wrote:
>
>> On Dec 12, 2012, at 3:03 AM, Andreas Grosam <agro...@onlinehome.de> 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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