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iOS

Posted by Stephen Hancocks
Stephen Hancocks
9,271 Points

Compare a property of an object in an array with a static number

I am really struggling to perform an 'if' statement on an array of data that I have parsed from HTML. I know the data is correct and the NSMutableArray contains 20 or so objects with properties "month" and "credits".

I want to check whether the credits are within certain ranges. I'm getting all sorts of errors

if([[_Credits objectAtIndex:18] valueForKey:@"credits"] > 10)

gives the errors "Ordered comparison between pointer and integer ('id' and 'int')" "Implicit conversion of 'int' to 'id' is disallowed with ARC

As the properties of my array objects are strings I thought it would help if I converted them to NSNumber. The conversion works fine [although it seems very long winded - a lot of the code I find on forums is for older iOS's]

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setPositiveFormat:@"###0.###"];
NSNumber *formattedStringNumber = [numberFormatter numberFromString:[[_credits objectAtIndex:18] valueForKey:@"credits"]];
NSLog(@"formattedNumberString: %@", formattedStringNumber);

Trying to compare formattedStringNumber throws up these issues

 if(formattedStringNumber > 10)

Implicit conversion of 'int' to NSNumber * is disallowed with ARC and Order comparison between pointer and integer ('NSNumber *' and 'int')

I really thought [and still hope] that there is an easily solution in my issue as I want to compare a lot of data against set targets.

Many thanks

Steve

5 Answers

eirikvaa
eirikvaa
18,015 Points

Check out this method from the NSString class:

- (int)intValue

It returns the integer value of the receiver's text.

You could use this method to convert the string object from your array to an integer value and then compare it. Hopefully no need for NSNumber objects.

Example:

NSString *string = @"5";
int value = [string intValue];
Stephen Hancocks
Stephen Hancocks
9,271 Points

Thanks. Just tried that [although with floatValue as I need decimal places] and it's work a treat. Three lines of code down to one is just what I wanted.

Thanks

eirikvaa
eirikvaa
18,015 Points

No problem. The feeling of finding the exact method you need is always good!

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points 
if(formattedStringNumber > 10)

try using this

    if(formattedStringNumber > @10)

which converts it to an NSNUmber literal.

Stephen Hancocks
Stephen Hancocks
9,271 Points

Just tried that. It gave a warning

'Direct comparison of a numeric literal has undefined behaviour'

and when I ran my code incorrectly as it returned that formattedStringNumber [2.5] was greater than 10.

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

ok try using 

if([formattedStringNumber intValue] > 10)

that will convert your nsnumber to an int, so you can use the comparison operator on it.

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

ok try using 

if([formattedStringNumber intValue] > 10)

that will convert your nsnumber to an int, so you can use the comparison operator on it.

Stephen Hancocks
Stephen Hancocks
9,271 Points
Stephen Hancocks
Stephen Hancocks
9,271 Points

I've removed the error by replacing the static number with a NSNumber variable that I declared.

 NSNumber *monthOne = @50;
 if(formattedStringNumber > monthOne)

I would still like a way to convert my array object property to an NSNumber in less than 4 lines of code. Can this be shortened at all?

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
[numberFormatter setPositiveFormat:@"###0.###"];
NSNumber *formattedStringNumber = [numberFormatter numberFromString:[[_personalCaseCredits objectAtIndex:18] valueForKey:@"caseCredits"]];
NSLog(@"formattedNumberString: %@", formattedStringNumber);