Objective c - Run block of code for X seconds but return immediately if condition satisfies

Question

So the situation is I need to run the code for 5 seconds but if I match the condition then want it to immediately return back. I am doing this in KIF test steps and I don't want this to block my applications main thread.

Sample pseudo Code -

+ (BOOL) isVerified:(NSString*)label;
{
     if(<condition match>)
        return YES;
    else if(X seconds not passed)
       <make sure m running this function for X seconds>
    else // X seconds passed now..
       return NO;
}

Answer 1

If you don't want to block the main thread in the case that NO should be returned after 5 sec delay, then structure that API asynchronously.

typedef void(^CCFVerificationCallbackBlock)(BOOL verified);

@interface CCFVerifier : NSObject

- (void)verifyLabel:(NSString *)label withCallbackBlock:(CCFVerificationCallbackBlock)block;

@end

static const int64_t ReturnDelay = 5.0 * NSEC_PER_SEC;

@implementation CCFVerifier

- (void)verifyLabel:(NSString *)label withCallbackBlock:(CCFVerificationCallbackBlock)block {
    NSParameterAssert(block);
    if( [label isEqualToString:@"moo"] )
        block(YES);
    else {
        dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, ReturnDelay);
        dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
            block(NO);
        });
    }
}
@end

To use:

_verifier = [[CCFVerifier alloc] init];
    [_verifier verifyLabel:@"foo" withCallbackBlock:^(BOOL verified) {
     NSLog(@"verification result: %d",verified);
}];