iOS does not scream at me when I pass in NULL or nil to the completion block in animateWithDuration:animations:completion: but does that mean it's okay? Or is it better to open an empty ^{ }?
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2 Answers
This is okay as long as you can trust that the code to which you are passing the nil won't try to call it as a block.
A quick demonstration:
typedef void (^GenericBlock)(void); void useThisBlock(GenericBlock block){ block(); } useThisBlock(^{NSLog(@"All okay.");}); useThisBlock(nil); // Compiles but crashes The inner code must check the block first: if( block ) block();
In the case of UIKit code, you should be fine.
Passing nil is fine, and in my opinion yields cleaner-reading code.
If you don't want to use a completion block, for this case you can also use the [UIView animateWithDuration:animations:] method.
3 Comments
pixelfreak
Thanks, I know there is a method without animation block. My question is more about block itself. So why
nil, not NULL?
sho
nil and NULL are equivalent. By convention, Objective-C typically uses nil where NULL is used in C.
Gabriele Petronella
that's not exactly true in ARC.
nil means object and must be used where id is expected, whereas NULL means a non-object non valid pointer and must be used where (void *) is expected. Take a look at this question for further information.