Invalid floating point comparison in Objective C - objective-c

Question

I have a weird dilema that I can't seem to place a finger on the issue and would like some outside assistance when trying to figure out the issue. I have a NSString value that I read in from a textbox and I convert it into a NSNumber. This works well and I get my value. Then I take my new number and I want to compare it with an array of 4 floating point numbers. However, when I try to compare I never get the proper results and this is where I am pulling my hair out. Below is a small snippet of code explaining my situation:
// THE FIRST IF STATEMENT IS WHAT GETS SELECTED
// newValue = 0.93
// colorRange = {0.10, 0.20, 0.80, 0.90 }
NSNumberFormatter *format = [[NSNumberFormatter alloc] init];
[format setNumberStyle:NSNumberFormatterDecimalStyle];
NSNumber *newValue = [format numberFromString:value];
[format release];
if (newValue < [colorRange objectAtIndex:0]) {
// Red background
selectedButton.backgroundColor = [UIColor redColor];
}
else if (newValue > [colorRange objectAtIndex:0] && newValue < [colorRange objectAtIndex:1]) {
// White background
selectedButton.backgroundColor = [UIColor whiteColor];
}
else if (newValue > [colorRange objectAtIndex:1] && newValue < [colorRange objectAtIndex:2]) {
// Black background
selectedButton.backgroundColor = [UIColor blackColor];
}
else if (newValue > [colorRange objectAtIndex:2] && newValue < [colorRange objectAtIndex:3]) {
// Blue background
selectedButton.backgroundColor = [UIColor blueColor];
}
else {
// Green background
selectedButton.backgroundColor = [UIColor greenColor];
}
What I am trying to do is see where my input value lies within my percentage range and select a color based on that information. If there is a more optimal way of doing this please let me know.

Answer 1

You can not compare NSNumbers directly like that, as you are comparing the values of their pointers. Instead, use the compare method of NSNumber to compare them like this:
if ([newValue compare:[colorRange objectAtIndex:0]] == NSOrderedAscending) {
// Red background
selectedButton.backgroundColor = [UIColor redColor];
}
...

Answer 2

I would do it in simple way:
if ([newValue floatVaue] < [colorRange objectAtIndex:0] floatValue])
And it is.

Answer 3

This (and the others like it):
newValue < [colorRange objectAtIndex:1]
Compares the pointer newValue to the pointer [colorRange objectAtIndex:1]. So it'll evaluate to non-zero if newValue happens to be lower down in memory.
Having been beaten to saying that by at least two posters, I'll take the time to propose the more compact method:
NSArray *backgroundColours = #[ [UIColor redColor], [UIColor whiteColor], ...];
NSUInteger index = 0;
for(NSNumber *colour in colorRange)
{
if([newValue compare:colour] == NSOrderedAscending)
{
selectedButton.backgroundColor = [backgroundColours objectAtIndex:index];
break;
}
index++;
}

Answer 4

You cannot compare NSNumber* objects using the < or > operators: it compares pointers, giving you arbitrary results. Use the compare: method instead:
if ([newValue compare:[colorRange objectAtIndex:0]] == NSOrderedAscending) ...
NSOrderedAscending means that the receiver is less than the argument
NSOrderedDescending means that the receiver is greater than the argument
NSOrderedSame means that the receiver is equal to the argument

Answer 5

As everybody else said you cannot compare pointers like that, just variables.
You could use
if ([newValue floatValue]<[[color objectAtIndex:0] floatValue]