1.变量存储的指针可变,变量存储的值不可变
//A modifiable pointer to a constant NSString (its value can't be modified) const NSString * str = @"11"; str = @"22";
2.变量存储的值可变,变量存储的指针不可变
//A constant pointer (not modifiable) to an NSString (its value can be modified) NSString *const str1 = @"33"; str1 = @"44"; //会报错
实例截图:
总结:
由于NSString是指针变量,因此只要保证NSString类型的变量存储的指针不可变就可以定义一个不可更改的NSString变量,定义方法: NSString *const str = @"111";
参考链接:
https://stackoverflow.com/questions/22953091/difference-between-nsstring-const-and-const-nsstring