Attempt to mutate immutable object error

Question

My code crashes at this line:

[(NSMutableString *)string replaceCharactersInRange:range withString:@""];

with the error attempt to mutate immutable object.

How is this happening and how do i fix it?

Now you're going back to reading a tutorial on typecasting in C. **Now.** — , Jan 26 '13 at 20:25

Ramy Al Zuhouri · Accepted Answer · 2013-01-26T20:34:42.520

7

The string isn't mutable, casting is not magic, it wouldn't turn it into a mutable string. You should do it on a mutable copy:

NSMutableString* mutableString= [string mutableCopy];
[mutableString replaceCharactersInRange:range withString:@""];

edited Jan 26 '13 at 20:34

answered Jan 26 '13 at 20:23

Ramy Al Zuhouri

2

+1 for "casting is not magic". I tend to say the exact same thing. – Jan 26 '13 at 20:24
1

Yes, but you probably want to store the mutable version in a variable first, or it won't do you much good. – Jesse Rusak Jan 26 '13 at 20:27

Anoop Vaidya · Answer 2 · 2013-01-26T20:27:15.663

3

You are typecasting an immutable string and then mutating it, actually this is not happening.

You need to create a new NSMutableString and then use replaceCharactersInRange...

NSMutableString *mutableString=[NSMutableString stringWithString:string];
[mutableString replaceCharactersInRange:range withString:@""];

If you want the result in same object set it to string.

string=mutableString;

edited Jan 26 '13 at 20:27

answered Jan 26 '13 at 20:24

Anoop Vaidya

2 Answers2