Traversing key/values of an NSDictionary, is enumerateKeysAndObjectsUsingBlock more efficient than looping keys and calling objectForkey:?

Question

I need to traverse all key/values pairs of a dictionary and do something with both fields. I am wondering what is more efficient, the traditional 'foreach key' approach or the blocks approach using enumerateKeysAndObjectsUsingBlock:.

Here you have an example:

Traditional approach (before blocks)

for (NSString* key in [self.dictionary allKeys] ) {
    [self processKey:key value: [self.dictionary objectForKey:value ]];
}

Blocks approach.

 [self.dictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop){
        [self processKey:key value:obj];
    }]; 

My gut feeling is that traversing the key/value pairs using the block is faster, but I am not sure since I don't know how dictionaries and the particular block method is implemented.

Any thoughts?

Thanks in advance!

Answer 1

They would be basically the same -- they are both synchronous traversals. However, the following would allow for concurrent traversal, which would be faster:

[self.dictionary enumerateKeysAndObjectsWithOptions:NSEnumerationConcurrent
                              usingBlock:^(id key, id object, BOOL *stop) {

}];