changing a key name in NSDictionary - objective-c

Question

I have a method which returns me a nsdictionary with certain keys and values. i need to change the key names from the dictionary to a new key name but the values need to be same for that key,but i am stuck here.need help

Answer 1

This method will only work with a mutable dictionary. It doesn't check what should be done if the new key already exists.
You can get a mutable dictionary of a immutable by calling mutableCopy on it.
- (void)exchangeKey:(NSString *)aKey withKey:(NSString *)aNewKey inMutableDictionary:(NSMutableDictionary *)aDict
{
if (![aKey isEqualToString:aNewKey]) {
id objectToPreserve = [aDict objectForKey:aKey];
[aDict setObject:objectToPreserve forKey:aNewKey];
[aDict removeObjectForKey:aKey];
}
}

Answer 2

You can't change anything in an NSDictionary, since it is read only.
How about loop through the dictionary and create a new NSMutableDictionary with the new key names ?

Answer 3

Could you not add a new key-value pair using the old value, and then remove the old key-value pair?
This would only work on an NSMutableDictionary. NSDictionarys are not designed to be changed once they have been created.

Answer 4

To change specific key to new key, I have written a recursive method for Category Class.
- (NSMutableDictionary*)replaceKeyName:(NSString *)old_key with:(NSString )new_key {
NSMutableDictionary dict = [NSMutableDictionary dictionaryWithDictionary: self];
NSMutableArray *keys = [[dict allKeys] mutableCopy];
for (NSString key in keys) {
if ([key isEqualToString:old_key]) {
id val = [self objectForKey:key];
[dict removeObjectForKey:key];
[dict setValue:val forKey:new_key];
return dict;
} else {
const id object = [dict objectForKey: key];
if ([object isKindOfClass:[NSDictionary class]]) {
[dict setObject:[dict replaceKeyName:old_key with:new_key] forKey:key];
} else if ([object isKindOfClass:[NSArray class]]){
if (object && [(NSArray)object count] > 0) {
NSMutableArray *arr_temp = [[NSMutableArray alloc] init];
for (NSDictionary *temp_dict in object) {
NSDictionary *temp = [temp_dict replaceKeyName:old_key with:new_key];
[arr_temp addObject:temp];
}
[dict setValue:arr_temp forKey:key];
}
}
}
}
return dict;
}