missing sentinel in method dispatch
[NSArray arrayWithObjects:@"cloudType", @"accessId", @"secretAccessKey"] //wrong
[NSArray arrayWithObjects:@"cloudType", @"accessId", @"secretAccessKey", nil] //correct
[NSArray arrayWithObjects:@"cloudType", @"accessId", @"secretAccessKey"] //wrong
[NSArray arrayWithObjects:@"cloudType", @"accessId", @"secretAccessKey", nil] //correct