Question

Sorry I realise this is a simple question but im new to iOS development and objective-c.

Coming from a c# background, I would try parse the string in the text box then if true assign it to an int to be used in a sum, then assign that to a label.

In iOS and obj-c im having some trouble with the above, and then what I would need to release and alloc.

Any help would be appreciated please.

Answer 1

You can use NSScanner to do that. For example:

NSString *test = @"45";
NSScanner *scanner = [[NSScanner alloc] initWithString:test];
NSInteger integer;
if ([scanner scanInteger:&integer])
{
    NSLog(@"The value is: %i", integer);
}
else
{
    NSLog(@"Didn't parse successfully.");
}

As another answer notes, you can use intValue or integerValue on NSString. There are a couple of things to note about that approach:

1. It returns 0 if the parse fails. This makes it impossible to determine if the value parsed was actually 0, or if the parse just failed.

2. Both NSScanner and intValue allow for whitespace, so     45 would parse successfully. With NSScanner, you can disable that if you desire by using setCharactersToBeSkipped to nil:

   [scanner setCharactersToBeSkipped:nil];
   

You can perform normal arithmetic from there on, like integer + 20, or sum other numbers that you’ve parsed.

If locale is important (See Julien’s answer), then you would use the setLocale method on NSScanner with an NSLocale for example, if we want to ensure the en-US locale is always used:

NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US"];
[scanner setLocale: locale];

---

what I would need to release and alloc.

That depends on quite a few things. Are you using ARC? If so then ARC will take care of the release for you. You may want to read up on memory management.