尝试更改不可变对象时发生错误 [英] ERROR for attempting mutating immutable object

问题描述

这是什么错误?我正在使用可变类型，但仍然无法正常工作！

What is this error? I am using mutable type but still it is not working!

错误是:

由于未捕获的异常而终止应用程序 'NSInvalidArgumentException'，原因:'不可变突变 具有deleteCharactersInRange的对象:'

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'mutate immutable object with deleteCharactersInRange:'

NSMutableString *line= [NSMutableString stringWithString:@"here is the string"];
[line deleteCharactersInRange: NSMakeRange(1,9 )];

推荐答案

我的新答案:

My new answer:

使用您的新代码，我在最后添加了一行:

With your new code, I added one extra line at the end:

NSMutableString *line= [NSMutableString stringWithString:@"here is the string"];
[line deleteCharactersInRange: NSMakeRange(1,9 )];
NSLog( @"line is %@", line );

控制台输出为:

2011-11-25 06:08:13.248 TestingCommandLine[13324:903] line is he string

没有引发异常.看起来对我有用！

No exception thrown. Looks like it's working for me!

我的原始答案(针对您的原始问题):

您不能从其中没有任何内容的行中删除字符(因此是例外).

You can't delete characters from a line that has nothing in it (hence the exception).

在这两行源代码之间，您是否还有其他代码?如果没有，则您有一个有效的NSMutableString ...，其中没有任何内容.而且，您不能从其中没有任何内容的可变字符串中删除任何内容.

Do you have any additional code between those two lines of source there? If not, you have a valid NSMutableString... with nothing in it. And you can't delete anything from a mutable string that has nothing in it.

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