NSDictionary *dictNull = @{@"key":[NSNull null]};
NSDictionary *dictNil = @{@"key":nil};//Collection element of type 'void *' is not an Objective-C object
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setValue:nil forKey:@"keyNil"];
[dict setObject:[NSNull null] forKey:@"keyNull"];
/* Send -setObject:forKey: to the receiver, unless the value is nil, in which case send -removeObjectForKey:.
*/
- (void)setValue:(nullable ObjectType)value forKey:(NSString *)key;
- (void)setObject:(ObjectType)anObject forKey:(id<NSCopying>)aKey;
Important
Raises an NSInvalidArgumentException if anObject is nil. If you need to represent a nil value in the dictionary, use NSNull.