相关疑难解决方法(0)

[attributedString enumerateAttributesInRange:range options:NSAttributedStringEnumerationReverse usingBlock:
     ^(NSDictionary *attributes, NSRange range, BOOL *stop) {

         NSMutableDictionary *mutableAttributes = [NSMutableDictionary dictionaryWithDictionary:attributes];
         [mutableAttributes setObject:[NSNumber numberWithInt:1] forKey:@"NSUnderline"];
         attributes = mutableAttributes;

     }];

我试图循环所有属性并添加NSUnderline给他们.在调试时,似乎NSUnderline被添加到字典中,但是当我第二次循环时它们被删除.我在更新NSDictionaries时做错了什么？