Question

我有一个业务对象，我需要更改其中一个属性。我尝试获取该属性的字符串表示然后修改它，就像我在尝试下面的代码

  NSMutableString *mutatingString = [ [ NSMutableString alloc ] init ] ;
  mutatingString = ( NSMutableString * ) [ businessOject valueForKey:@"basicproperty" ] ;
  [ mutatingString appendString:@"Modified" ];

当我在appendString的第三行加热时，我得到以下异常：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 
   'Attempt to mutate immutable object with appendString:'

我的代码出了什么问题？

Answer 1

您不应将[businessOject valueForKey：@“basicproperty”]的结果从NSString *转换为NSMutableString *。

NSString* str  =   [businessOject valueForKey:@"basicproperty" ];
NSMutableString *mutatingString = [[NSMutableString alloc ] initWithString:str  ] ;
[mutatingString appendString:@"Modified" ];
[businessOject setValue:mutatingString forKey:@"basicproperty" ]

在ios中归档unarchiving，如何处理错误？

1 个答案: