OC NSString总结

1、初始化

2、常用方法

拼接字符串

判断是否相同字符串

　　[answer isEqualToString:self.currentModel.answer]//answer==self.currentModel.answer区别

3、方法的比较

NSSttring　　stringByAppendingString 　　//NSString不可变，每次append生成新的NSString

NSMulbtbleString　　appendString　　　　//NSMulbtbleString操作自身

 1 __block NSString * answer = [NSString new];
 2 [self.answerView.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
 3         UIButton * button = (UIButton*)obj;
 4         answer = [answer stringByAppendingString:button.currentTitle];
 5     }];
 6
 7
 8
 9 __block NSMutableString * answer = [NSMutableString string];
10     [self.answerView.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
11         UIButton * button = (UIButton*)obj;
12         [answer appendString:button.currentTitle];
13     }];