Implementing a method taking a block to use as callback
Objective CIosCallbackObjective C-BlocksObjective C Problem Overview
I would like to write a method similar to this:
+(void)myMethodWithView:(UIView *)exampleView completion:(void (^)(BOOL finished))completion;
I've basically stripped down the syntax taken from one of Apple's class methods for UIView
:
+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion;
And would expect it to be used like so:
[myFoo myMethodWithView:self.view completion:^(BOOL finished){
NSLog(@"call back success");
}];
My question is how can I implement this? If someone can point me to the correct documentation that would be great, and a very basic example would be much appreciated (or a similar answer on Stack Overflow -- I couldn't find one). I still don't quite know enough about delegates to determine whether that is even the correct approach!
I've put a rough example of what I would have expected it to be in the implementation file, but as I can't find info it's guess work.
+ (void)myMethod:(UIView *)exampleView completion:(void (^)(BOOL finished))completion {
// do stuff
if (completion) {
// what sort of syntax goes here? If I've constructed this correctly!
}
}
Objective C Solutions
Solution 1 - Objective C
You can call a block like a regular function:
BOOL finished = ...;
if (completion) {
completion(finished);
}
So that means implementing a complete block function using your example would look like this:
+ (void)myMethod:(UIView *)exampleView completion:(void (^)(BOOL finished))completion {
if (completion) {
completion(finished);
}
}
Solution 2 - Objective C
I would highly recommend that you read up on Blocks to understand what is happening.
Solution 3 - Objective C
If you're specially looking for a doc, to create custom method using blocks, then the following link is the one which explains almost everything about it. :)
http://developer.apple.com/library/ios/documentation/cocoa/Conceptual/Blocks/Articles/bxUsing.html
I happen to answer quite a same question recently, have a look at this: https://stackoverflow.com/questions/5486976/objective-c-declare-a-block-method-parameter-without-using-a-typedef/7397430#7397430