NSDictionary Key For Value/Object?

问题:

Can we get the key for an object in an NSDictionary by passing a particular value or object?

回答1:

-[NSDictionary allKeysForObject:] returns an NSArray of all the keys whose objects match the passed object, where "match" is determined by isEqual:.

回答2:

To answer you question in a more specific manner, use the following to get a key for a particular object:

NSString *knownObject = @"the object";
NSArray *temp = [dict allKeysForObject:knownObject];
NSString *key = [temp lastObject];

//"key" is now equal to the key of the object you were looking for

回答3:

This is how you can get a first key for object (in case it is an NSString):

NSArray *keys = [yourDic allKeysForObject:yourObject];
NSString *yourKey;
if ([keys count] > 0) {
   yourKey = keys[0];
}

This handles if the object is not found in in the dictionary.