nsrunloop_example.m

// wait until completion functions get called by method inside loop.

for(Object *o in objects) 
{
    __block BOOL block = YES;
    
    [self applyMethod:o success:^(id result) {
        //...
        block = NO;
    } failure:^(NSError *error) {
        //...
        block = NO;
    }];
    
    while (block)
    { [[NSRunLoop mainRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]; }
}