How do I specify the block object / predicate required by NSDictionary's keysOfEntriesPassingTest ?
- by Todd
For learning (not practical -- yet) purposes, I'd like to use the following method on an NSDictionary to give me back a set of keys that have values using a test I've defined. Unfortunately have no idea how to specify the predicate.
NSDictionary keysOfEntriesPassingTest:
- (NSSet *)keysOfEntriesPassingTest:(BOOL (^)(id key, id obj, BOOL *stop))predicate
Let's say for example all my values are NSURLs, and I'd like to get back all the URLs that are on port 8080. Here's my stab at coding that -- though it doesn't really make sense to me that it'd be correct:
NSSet * mySet = [myDict keysOfEntriesPassingTest:^(id key, id obj, BOOL *stop) {
if( [[obj port] isEqual: [NSNumber numberWithInt: 8080]]) {
return key;
}]
And that's because I get back the following compiler error:
incompatible block pointer types initializing 'void (^)(struct objc_object *, struct objc_object *, BOOL *)', expected 'BOOL (^)(struct objc_object *, struct objc_object *, BOOL *)'
What am I missing? I'd appreciate a pointer at some docs that go into more detail about the "Block object" that the predicate is supposed to be.
Thanks!
