Primitive number types and custom editors (was: Re: [grails-user] Grails 1.0.4 snapshot available)

[Peter Ledbrook]

>> Earlier it was rendered as "12.34". Nice but...
>> When I save the form I get the following validation error:
>> Failed to convert property value of type [java.lang.String] to required type
>> [float] for property weight; nested exception is
>> java.lang.NumberFormatException: For input string: "12,34"
>
> Thanks for the report. I'll take a look.

Unfortunately, it seems that the custom number editor cannot be
registered for primitive "float" fields. To be honest, you should be
using BigDecimal wherever the user can enter numbers, but it would
still be nice if this worked :( Does anyone know whether it's possible
to register custom data binders for primitive types?

Thanks,

Peter

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[Peter Ledbrook]

> Unfortunately, it seems that the custom number editor cannot be
> registered for primitive "float" fields. To be honest, you should be
> using BigDecimal wherever the user can enter numbers, but it would
> still be nice if this worked :( Does anyone know whether it's possible
> to register custom data binders for primitive types?

OK, I worked it out - now fixed. Please note that you should still use
BigDecimal otherwise the value entered by the user may not be the
value shown by the application!

Cheers,

Peter

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[Dimo Velev]

Hi Peter,

what about doubles? Could you elaborate on this float vs. BigDecimal issue?

Thanks,
Dimo
Peter Ledbrook wrote:

>> Unfortunately, it seems that the custom number editor cannot be
>> registered for primitive "float" fields. To be honest, you should be
>> using BigDecimal wherever the user can enter numbers, but it would
>> still be nice if this worked :( Does anyone know whether it's possible
>> to register custom data binders for primitive types?
>>    
>
> OK, I worked it out - now fixed. Please note that you should still use
> BigDecimal otherwise the value entered by the user may not be the
> value shown by the application!
>
> Cheers,
>
> Peter
>
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[Peter Ledbrook]

> what about doubles? Could you elaborate on this float vs. BigDecimal issue?

Same with doubles. There are some numbers (such as 1.1 I believe) that
cannot be represented exactly by a double. So if you had a double
field and the user entered 1.1 into the scaffolded edit page, the show
page may display 1.099998 or something like that. If you need exact
floating-point representation then you should use BigDecimal. In fact,
floating-point literals in Groovy are instances of BigDecimal rather
than float or double.

If you then need to do some calculations using your floating-point
fields, you can convert them to doubles or floats first and then
convert them back to BigDecimal for storage.

Hope that helps,

Peter

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[Robert Fischer]

Read up on the care and feeding of floating point numbers, or you're going to have a lot of nasty
surprises if you're using floats/doubles in your code.

For instance: 1.0/7.0*7.0 != 1.0

~~ Robert.

Dimo Velev wrote:

> Hi Peter,
>
> what about doubles? Could you elaborate on this float vs. BigDecimal issue?
>
> Thanks,
> Dimo
> Peter Ledbrook wrote:
>>> Unfortunately, it seems that the custom number editor cannot be
>>> registered for primitive "float" fields. To be honest, you should be
>>> using BigDecimal wherever the user can enter numbers, but it would
>>> still be nice if this worked :( Does anyone know whether it's possible
>>> to register custom data binders for primitive types?
>>>    
>>
>> OK, I worked it out - now fixed. Please note that you should still use
>> BigDecimal otherwise the value entered by the user may not be the
>> value shown by the application!
>>
>> Cheers,
>>
>> Peter
>>
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>
>
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--
~~ Robert Fischer.
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