NSMutableString为null - 此代码有什么问题

Question

新手问题...... 有人可以告诉我为什么＆＃39;得分的价值＆＃39;一片空白？有什么不对，什么不明白？我试图将UILabel文字设置为＆＃39;得分＆＃39;

MSMutableString *score
[score appendFormat:@"Score : %@,[[NSString stringWithFormat:@"%f",19.5]
   RoundNumberFromString:[NSString stringWithFormat:@"%f",19.5]]];

NSLog(@"%f",score)    <-- WHY IS THIS NIL?

然后UILabel空白＆＃39;

事先提前

Answer 1

init score var before - score = [NSMutableString string]