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Editorial Team
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Asked: 2026-05-18T22:47:56+00:00

I’m building a url dynamically and needed a way to add an NSNumber’s intValue

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I’m building a url dynamically and needed a way to add an NSNumber’s intValue to the end of it.

NSNumber *hatId = [NSNumber NumberWithInt:25]
NSMutableString* theUrlString = [[NSMutableString alloc] init];
[theUrlString appendFormat:@"http://www.website.com/SelectHat/%d", [hatid intValue]];
NSURL *url = [NSURL URLWithString:theUrlString];

After doing the above a simple unit test or NSLog will show the result looks valid

http://www.website.com/SelectHat/25

But my question is this – does concatenation in this way alter the NSString so it’s no long a valid string like I would expect? also is this a “good” way to build a string that needs the intValue from an NSNumber?

Update

I just wanted to make sure the %d inline was no problem and the NSString was as I expected it would be. The issue I’m having is a bit more complex so I’ll save that for another question. Thanks for the replies about NSURL / NSNumber / int as I’m still learning a great deal about objective-c

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1 Answer

  1. Editorial Team

    I’m curious why you think appending content to a mutable string would make that string invalid. If you’re having a problem please share what’s actually going wrong.

    [theUrlString appendFormat:@"http://www.website.com/SelectHat/%d", [hatid intValue]];

    Is valid and a fine way to modify a NSMutableString.

    Since you’re building a URL you might want to use NSURL directly instead. Look at +URLWithString:realtiveToURL: and -URLByAppendingPathComponent: as ways to build a NSURL. Those methods can be convenient because they will prevent you from accidentally creating a string ending in “SelectHat25” or “SelectHat//25” when you wanted “SelectHat/25”.

    Now strings and URLs aside

    NSNumber* hatid = 25;

    is not valid. That’s creating a pointer to an NSNumber object and assigning it to an int value. You’ll be looking for a NSNumber object at memory address ’25’ and who knows what you’ll find there. You should be constructing an instance of NSNumber instead or just using an int type.

    NSNumber* hatid = [[NSNumber alloc] initWithUnsignedInteger:25];

NSUInteger hatid = 25
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