Weird behaviour on Numeric Stepper decimals

Question

I am making an editor for a field with numbers. I tried a text field, but since it's a Number datatype coming in, it didn't go smoothly -- despite recasting strings as numbers etc.. it kept giving me NaN as the value. So I decided it would be best to go with a numeric stepper.

When I initially loaded it up it would drop all my decimals and only display my numbers as integers. I changed the stepIncrement to 0.1 and now it does show the decimals (a weird requirement imo).. but when I step up it occasionally gives me a value like '17.700000000000003' when I would expect 17.7. All of the numbers in my data have a single decimal place. I know I can write a dataformatter, but it seems like it shouldn't be necessary in this situation.

Is there another way I could deal with this?

Answer 1

You've stumbled upon the compromise of trying to represent decimal numbers in floating point binary formats like IEEE 754. Not all decimal numbers can be exactly represented. You can read up on this issue in great detail here:

http://en.wikipedia.org/wiki/Floating_point#Representable_numbers.2C_conversion_and_rounding

You can use Number.toFixed(fractionDigits:uint) to display to an arbitrary number of decimal places.

Answer 2

in your MXML

<s:NumericStepper  valueFormatFunction="stepperFormatter"/>

in your script

protected function stepperFormatter(newValue:Number):String
{
    return Math.ceil(newValue).toString()
}

Answer 3

You can use the valueFormatFunction which takes the numeric value and formats it to a string. You will need to set explicit widths on your numeric steppers to make they fit though.