Automatically trim NSString in custom setter? - objective-c

Question

I have an object w/ an NSString for a property. I would like to use a custom setter for this property so that it always trims all whitespace when the string is set.
Normally this is done with NSString *blah2 = [blah stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];, but I'm not sure about how to formulate this for a custom setter. Isn't it bad to use autoreleased objects like this in the setter? Should I use a mutable string instead and then convert it to unmutable?
Thanks for any help you guys can provide.

Answer 1

I'm going to presume ARC.
#import <Foundation/Foundation.h>
#interface Foo:NSObject
#property (nonatomic,copy) NSString *myString;
#end
#implementation Foo
#synthesize myString = _myString;
- (void)setMyString:(NSString *)aString;
{
_myString = [[aString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] copy];
}
#end
int main(int argc, char *argv[]) {
#autoreleasepool {
Foo *someFoo = [[Foo alloc] init];
someFoo.myString = #"Blah ";
NSLog(#"Length = %ld",[[someFoo myString] length]); // prints 4
}
}
In the setter, I do copy the parameter of the setter in the event someone tries to provide an instance of NSMutableString - presuming that Foo is not expected to modify the original string.
EDIT:
Or if manual reference counting, the setter might be:
- (void)setMyString:(NSString *)aString;
{
if( aString != _myString ) {
[_myString release];
_myString = [[aString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] copy];
}
}