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

__block NSString * answer = [NSString new];
[self.answerView.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        UIButton * button = (UIButton*)obj;
        answer = [answer stringByAppendingString:button.currentTitle];
    }];



__block NSMutableString * answer = [NSMutableString string];
    [self.answerView.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        UIButton * button = (UIButton*)obj;
        [answer appendString:button.currentTitle];
    }];