NSDictionary

[NSDictionary dictionaryWithObject:@"1" forKey:@"a"];
[NSDictionary dictionaryWithObjectsAndKeys:@"1",@"a",@"2",@"b",nil];
[NSDictionary dictionaryWithObjects:[NSArray arraywithObjects:@"1",@"2", nil] forKey:[NSArray arrayWithObjects:@"a",@"3",nil]];
NSDictionary *dic4 = @{@"1":@"a",@"2":@"b"};
[dic addEntriesFromDictionary:@{@"1":@"a",@"2":@"b"}];