You need to use NSMutableString
NSMutableString *mu = [NSMutableString stringWithString:dir];
[mu insertString:@" " atIndex:5];
or you could use those method to split your string :
– substringFromIndex:
– substringWithRange:
– substringToIndex:
and recombine them after with
– stringByAppendingFormat:
– stringByAppendingString:
– stringByPaddingToLength:withString:startingAtIndex:
But that way is more trouble that it’s worth. And since NSString is immutable, you would bet lot of object creation for nothing.
NSString *s = @"abcdefghijklmnop";
NSMutableString *mu = [NSMutableString stringWithString:s];
[mu insertString:@" || " atIndex:5];
// This is one option
s = [mu copy];
//[(id)s insertString:@"er" atIndex:7]; This will crash your app because s is not mutable
// This is an other option
s = [NSString stringWithString:mu];
// The Following code is not good
s = mu;
[mu replaceCharactersInRange:NSMakeRange(0, [mu length]) withString:@"Changed string!!!"];
NSLog(@" s == %@ : while mu == %@ ", s, mu);
// ----> Not good because the output is the following line
// s == Changed string!!! : while mu == Changed string!!!
Which can lead to difficult to debug problems.
That is the reason why @property for string are usually define as copy so if you get a NSMutableString, by making a copy you are sure it won’t change because of some other unexpected code.
I tend to prefer s = [NSString stringWithString:mu]; because you don’t get the confusion of copying a mutable object and having back an immutable one.