Block

#Block

##What is a block?

A block of code (i.e. a sequence of statements inside {}).

##What does it look like?

Here’s an example of calling a method that takes a block as an argument.

NSString *stopKey = [@“Enough” uppercaseString];
__block BOOL stoppedEarly = NO;
double stopValue = 53.5;
[aDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id value, BOOL *stop) {
    NSLog(@“value for key %@ is %@”, key, value);
    if ([stopKey isEqualToString:key] || ([value doubleValue] == stopValue)) {
		*stop = YES;
        stoppedEarly = YES;  // this is legal now
    }
}];
if (stoppedEarly) NSLog(@“I stopped logging dictionary values early!”);

stoppedEarly will copy to heap and set in block,then set in stack agagin until block finished

stopKey will automatically have a strong pointer to it until the block goes out of scope This is obviously necessary for the block to function properly