Rails core - Mar 2006 - Why is FormHelper using value_before_type_cast ?

Hi !

Just wondering here, because if I define reader methods, then these
aren't used in the forms.

For example, I have this:
class Customer
  def tax_rate
    (read_attribute(:tax_rate) * 100.0).to_i
  end

  def tax_rate=(rate)
    write_attribute(:tax_rate, rate / 100.0)
  end
end

<%= text_field :customer, :tax_rate %>

For 7.5, the value shown on screen is 750.  Of course, I could do:
<%= text_field :customer, :tax_rate, :value => @customer.tax_rate %>

but that gets pretty boring real quick...

So, what is the rationale behind this decision ?  Are the date/time
helpers the ones that need the value_before_type_cast ?

Thanks !
--
François Beausoleil
http://blog.teksol.info/

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On 3/6/06, Francois Beausoleil <francois.beausoleil@gmail.com>
wrote:
> Hi !
>
> Just wondering here, because if I define reader methods, then these
> aren''t used in the forms.
>
> For example, I have this:
> class Customer
>   def tax_rate
>     (read_attribute(:tax_rate) * 100.0).to_i
>   end
>
>   def tax_rate=(rate)
>     write_attribute(:tax_rate, rate / 100.0)
>   end
> end
>
> <%= text_field :customer, :tax_rate %>
>
> For 7.5, the value shown on screen is 750.  Of course, I could do:
> <%= text_field :customer, :tax_rate, :value => @customer.tax_rate
%>
>
> but that gets pretty boring real quick...
>
> So, what is the rationale behind this decision ?  Are the date/time
> helpers the ones that need the value_before_type_cast ?
Otherwise the user''s data will be ''randomly'' changed
by the system.   i.e.

irb(main):001:0> "asdifjasdliofj".to_i
=> 0
irb(main):002:0> "123,40".to_i
=> 123

So if it didn''t use _before_typecast, and the user typed either of
those values, then when the page was re-rendered,  the values won''t
have been remembered correctly.

The previous behaviour was worse and led to many bug reports about 0
appearing where it wasn''t expected.

--
Cheers

Koz

2006/3/5, Michael Koziarski
<michael@koziarski.com>:
> On 3/6/06, Francois Beausoleil <francois.beausoleil@gmail.com> wrote:
> > class Customer
> >   def tax_rate
> >     (read_attribute(:tax_rate) * 100.0).to_i
> >   end
> >
> >   def tax_rate=(rate)
> >     write_attribute(:tax_rate, rate / 100.0)
> >   end
> > end
>
> Otherwise the user's data will be 'randomly' changed by the
system.   i.e.
>
> irb(main):001:0> "asdifjasdliofj".to_i
> => 0
> irb(main):002:0> "123,40".to_i
> => 123
>
> So if it didn't use _before_typecast, and the user typed either of
> those values, then when the page was re-rendered,  the values won't
> have been remembered correctly.
How can custom reader/writer methods be accomodated then ?

Thanks !
--
François Beausoleil
http://blog.teksol.info/

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> How can custom reader/writer methods be accomodated then ?
>
See
http://dev.rubyonrails.org/browser/trunk/activerecord/lib/active_record/base.rb#L1561

if you implement your own _before_type_cast methods you should be
fine.   Why not just define a separate accessor  though,  i.e. one
used during calculations but not during user input?

--
Cheers

Koz

2006/3/5, Michael Koziarski
<michael@koziarski.com>:
> See
http://dev.rubyonrails.org/browser/trunk/activerecord/lib/active_record/base.rb#L1561
>
> if you implement your own _before_type_cast methods you should be
> fine.   Why not just define a separate accessor  though,  i.e. one
> used during calculations but not during user input?
I WANT the value to be displayed as 7.50, not 750 ! 
#***_before_type_cast returns the latter, which is incorrect from the
user's point of view.  He really typed 7.5, but the value is stored as
750, to ensure floating point values are not modified along the way.

So, if I override tax_rate_before_type_cast, I should be all right ? 
I'll test this out.

Thanks for the info, Michael.

Bye !
--
François Beausoleil
http://blog.teksol.info/

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