先看代码
@property(nonatomic,copy) NSMutableString *mutableStringCpoyName;
NSMutableString *mutabString = [NSMutableString stringWithFormat:@"a1234567890"];
self.mutableStringCpoyName = mutabString;
[self.mutableStringCpoyName appendString:@"C变了"];
总结
copy之后就是不可变对象,这个时候使用appendString 会报奔溃Attempt to mutate immutable object with appendString:'(尝试使用 appendString 改变不可变对象：)
