Rails - Jan 2011 - Help How to create DSL for conditional validations

Hi All,

I am new to Ruby and ROR
I were trying to create small DSL for conditional validations

 valid_with_cond :bypass_validation do
   if self.addresses > 3
      errors[:base] << "Can not have more than 3 addresses".
   end
 end


By this I wanted to create array of method and call them all in custom
validation method.

this above code I wanted to do

 attr_accessor :bypass_validation

 def svalid_cond
   unless bypass_validation
     if self.addresses > 3
        errors[:base] << "Can not have more than 3 addresses".
     end
   end
 end

           This way I want in new and edit form I can ask user to click
           :bypass_validation attribute and I will bypass this validation.

I tried to create


 def valid_with_cond(name, &block)
   attr_accessor name
   define_method "svalidator_#{name}" do |*arg|
     if send name
       yield *arg
     end
   end
 end


But after trying it in

Class Person < ActibeRecord::Base
 valid_with_cond :test do
     if self.addresses > 3
        errors[:base] << "Can not have more than 3 addresses".
   end
 end
end


But when I check it on console

Person.test

it throw me error test is private method.

Anybody could let me know how to correct it.



--
Regards,
-sharad

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On Jan 8, 10:18 pm, Sharad Pratap
<sh4...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> Class Person < ActibeRecord::Base
>  valid_with_cond :test do
>      if self.addresses > 3
>         errors[:base] << "Can not have more than 3
addresses".
>    end
>  end
> end
>
> But when I check it on console
>
> Person.test
>
> it throw me error test is private method.
>
> Anybody could let me know how to correct it.
>
Your call to attr_accessor will create instance methods called test
and test=, but you tried to call test on the class (and so you end up
falling through to Kernel#test).
Have you seen that validations take :if and :unless options ?

Fred

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Hi
> Your call to attr_accessor will create instance methods called test
> and test=, but you tried to call test on the class (and so you end up
> falling through to Kernel#test).
No I have tested this is not the case, yes I have given wrong example
but with object also it is not working, I have given all details below
I guess I got it working by hit and trial way, so not sure what
exactly is happening around.
> Have you seen that validations take :if and :unless options ?
I need to use coustom validation, for them I did not see any :if,
:unless option

But as I got it working I have lot of question in all stages
that I want to put else I will never able to know what is happening.

test 1:
    ruby>
    ruby>     def cvalidation(name, &block)
    ruby>       attr_accessor name
    ruby>       define_method "svalidator_#{name}" do |*arg|
    ruby>             if send name
    ruby>               yield *arg
    ruby>             end
    ruby>         end
    ruby>     end
     =>
    ruby>
    ruby>   class Person
    ruby>   cvalidation :zen do
    ruby>       puts "Yes"
    ruby>     end
    ruby>   end
           => #<Proc:0x95e73fc@(irb):8 (lambda)>
    ruby> x = Person.newq
          NoMethodError: undefined method `newq'' for Person:Class

So this is not working now in test 2,  I now test only attr_accessor

test 2:

    ruby>   def k(name)
    ruby>    attr_accessor name
    ruby>   end
            => nil
    ruby>  class Personq
    ruby>   k :test
    ruby>   end
           => nil
    ruby>  x = Personq.new
           => #<Personq:0x917a4e0>
    ruby>  x.test
           NoMethodError: private method `test'' called for
#<Personq:
0x917a4e0>

it again will not work.


test 3:
    ruby>  def k(name)
    ruby>     class_eval do
    ruby>       attr_accessor name
    ruby>     end
    ruby>  end
             => nil
    ruby> class Pers
    ruby>   k :u
    ruby> end
    ruby> x = Pers.new
           => #<Pers:0x8f9bf0c>
    ruby> x.u
           => nil
    ruby> x.u = "sfdsg"
          => "sfdsg"
    ruby> x.u
          => "sfdsg


Q1: Now it is working, but why it did not work in test 2 ?



test 4:
    ruby>   def cvalidation(name, &block)
    ruby>       class_eval do
    ruby>             attr_accessor name
    ruby>           define_method "svalidator_#{name}" do |*arg|
    ruby>                 if name
    ruby>                   yield *arg
    ruby>                 end
    ruby>             end
    ruby>         end
    ruby>     end
              => nil
    ruby>
    ruby> class Work
    ruby>   cvalidation :done do
    ruby>       puts "Yes"
    ruby>     end
    ruby>   end
            => #<Proc:0xa337638@(irb):64 (lambda)>
    ruby> x = Work.new
           => #<Work:0xa32d200>
    ruby> x.svalidator_done
          Yes
           => nil
    ruby> x.done
          => nil

Here define_method is working but it is not using argument `name'' in
if condition, it uses some other name method, than provided argument
`name''

Q2: Why it is like that and what `name'' method or variable it is
    actually using in both lines ?
    ruby>           define_method "svalidator_#{name}" do |*arg|
    ruby>                 if name


test 5:
    ruby>   def cvalidation(name, &block)
    ruby>       class_eval do
    ruby>             attr_accessor name
    ruby>           define_method "svalidator_#{name}" do |*arg|
    ruby>                 if send "#{name}"
    ruby>                   yield *arg
    ruby>                 end
    ruby>             end
    ruby>         end
    ruby>     end
              => nil
    ruby>
    ruby>   class QQ
    ruby>     cvalidation :xx do
    ruby>       puts "Yes"
    ruby>     end
    ruby>   end
            => #<Proc:0xa0aaf28@(irb):105 (lambda)>
    ruby> x = QQ.new
          => #<QQ:0xa0a09ec>
    ruby> x.svalidator_xx
          => nil
    ruby> x.xx
          => nil
    ruby> x.xx = "sfddsaf"
          => "sfddsaf"
    ruby> x.svalidator_xx
          Yes
          => nil
    ruby> x.xx = nil
          => nil
    ruby> x.svalidator_xx
          => nil
    ruby> class NN
    ruby>   cvalidation :ww do |w|
    ruby>       puts w, " Hi"
    ruby>     end
    ruby>   end
            => #<Proc:0x9fbe830@(irb):105 (lambda)>
    ruby> x = NN.new
          => #<NN:0x9fabb40>
    ruby> x.ww
          => nil
    ruby> x.svalidator_ww
          => nil
    ruby> x.ww = "Sharad"
          => "Sharad"
    ruby> x.svalidator_ww

          Hi
          => nil
    ruby> x.svalidator_ww "Sharad"
          Sharad
          Hi
          => nil
    ruby> puts "Sharad", "Hi"
          Sharad
          Hi
          => nil
    ruby>


Here I guess as I see all is working, but
I really like to know about `name'' used in

    ruby>                 if send "#{name}"

in test 5, uses the `name'' arguemnt provided.

But
    ruby>                 if name
in test 4 it do not able to use same `name'' argument

Why ?

--
Regards,
-sharad


On Jan 9, 3:37 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On Jan 8, 10:18 pm, Sharad Pratap
<sh4...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
>
>
> > Class Person < ActibeRecord::Base
> >  valid_with_cond :test do
> >      if self.addresses > 3
> >         errors[:base] << "Can not have more than 3
addresses".
> >    end
> >  end
> > end
>
> > But when I check it on console
>
> > Person.test
>
> > it throw me error test is private method.
>
> > Anybody could let me know how to correct it.
>
> Your call to attr_accessor will create instance methods called test
> and test=, but you tried to call test on the class (and so you end up
> falling through to Kernel#test).
> Have you seen that validations take :if and :unless options ?
>
> Fred
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On Jan 9, 1:22 pm, sharad <sh4...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
> > Have you seen that validations take :if and :unless options ?
>
> I need to use coustom validation, for them I did not see any :if,
> :unless option
I think you can still do

validate :something, :if => :something+else?
>
> But as I got it working I have lot of question in all stages
> that I want to put else I will never able to know what is happening.
>
[snip
>     ruby>
>     ruby>   class Person
>     ruby>   cvalidation :zen do
>     ruby>       puts "Yes"
>     ruby>     end
>     ruby>   end
>            => #<Proc:0x95e73fc@(irb):8 (lambda)>
>     ruby> x = Person.newq
>           NoMethodError: undefined method `newq'' for Person:Class
Not sure what this is showing - you haven''t attempted to define newq
anywhere
>
> So this is not working now in test 2,  I now test only attr_accessor
>
> test 2:
>
>     ruby>   def k(name)
>     ruby>    attr_accessor name
>     ruby>   end
>             => nil
>     ruby>  class Personq
>     ruby>   k :test
>     ruby>   end
>            => nil
>     ruby>  x = Personq.new
>            => #<Personq:0x917a4e0>
>     ruby>  x.test
>            NoMethodError: private method `test'' called for
#<Personq:
> 0x917a4e0>
>
I ran this in irb and this worked fine.
> test 4:
>     ruby>   def cvalidation(name, &block)
>     ruby>       class_eval do
>     ruby>             attr_accessor name
>     ruby>           define_method "svalidator_#{name}" do
|*arg|
>     ruby>                 if name
>     ruby>                   yield *arg
>     ruby>                 end
>     ruby>             end
>     ruby>         end
>     ruby>     end
>               => nil
>     ruby>
>     ruby> class Work
>     ruby>   cvalidation :done do
>     ruby>       puts "Yes"
>     ruby>     end
>     ruby>   end
>             => #<Proc:0xa337638@(irb):64 (lambda)>
>     ruby> x = Work.new
>            => #<Work:0xa32d200>
>     ruby> x.svalidator_done
>           Yes
>            => nil
>     ruby> x.done
>           => nil
>
> Here define_method is working but it is not using argument `name''
in
> if condition, it uses some other name method, than provided argument
> `name''
>
> Q2: Why it is like that and what `name'' method or variable it is
>     actually using in both lines ?
blocks are closures, so it sees the same local variables as those that
were existent when define_method were called, so it picks up the name
that was first argument to cvalidation. self is special though - self
will be the value of the object the method is called on.
>     ruby>           define_method "svalidator_#{name}" do
|*arg|
>     ruby>                 if name
>
> test 5:
>     ruby>   def cvalidation(name, &block)
>     ruby>       class_eval do
>     ruby>             attr_accessor name
>     ruby>           define_method "svalidator_#{name}" do
|*arg|
>     ruby>                 if send "#{name}"
>     ruby>                   yield *arg
>     ruby>                 end
>     ruby>             end
>     ruby>         end
>     ruby>     end
>               => nil
>     ruby>
>     ruby>   class QQ
>     ruby>     cvalidation :xx do
>     ruby>       puts "Yes"
>     ruby>     end
>     ruby>   end
>             => #<Proc:0xa0aaf28@(irb):105 (lambda)>
>     ruby> x = QQ.new
>           => #<QQ:0xa0a09ec>
>     ruby> x.svalidator_xx
>           => nil
>     ruby> x.xx
>           => nil
>     ruby> x.xx = "sfddsaf"
>           => "sfddsaf"
>     ruby> x.svalidator_xx
>           Yes
>           => nil
>     ruby> x.xx = nil
>           => nil
>     ruby> x.svalidator_xx
>           => nil
>     ruby> class NN
>     ruby>   cvalidation :ww do |w|
>     ruby>       puts w, " Hi"
>     ruby>     end
>     ruby>   end
>             => #<Proc:0x9fbe830@(irb):105 (lambda)>
>     ruby> x = NN.new
>           => #<NN:0x9fabb40>
>     ruby> x.ww
>           => nil
>     ruby> x.svalidator_ww
>           => nil
>     ruby> x.ww = "Sharad"
>           => "Sharad"
>     ruby> x.svalidator_ww
>
>           Hi
>           => nil
>     ruby> x.svalidator_ww "Sharad"
>           Sharad
>           Hi
>           => nil
>     ruby> puts "Sharad", "Hi"
>           Sharad
>           Hi
>           => nil
>     ruby>
>
> Here I guess as I see all is working, but
> I really like to know about `name'' used in
>
>     ruby>                 if send "#{name}"
>
> in test 5, uses the `name'' arguemnt provided.
>
> But
>     ruby>                 if name
> in test 4 it do not able to use same `name'' argument
>
When you just write name, it picks up the local variable from the
closure (it''s ambiguous whether you mean the local variable or the
method, and in these cases ruby picks the local variable), but by
using send you''re forcing it to call the accessor method. You could
also have disambiguated by writing self.name or name()

Fred
> Why ?
>
> --
> Regards,
> -sharad
>
> On Jan 9, 3:37 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> wrote:
>
>
>
> > On Jan 8, 10:18 pm, Sharad Pratap
<sh4...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > Class Person < ActibeRecord::Base
> > >  valid_with_cond :test do
> > >      if self.addresses > 3
> > >         errors[:base] << "Can not have more than 3
addresses".
> > >    end
> > >  end
> > > end
>
> > > But when I check it on console
>
> > > Person.test
>
> > > it throw me error test is private method.
>
> > > Anybody could let me know how to correct it.
>
> > Your call to attr_accessor will create instance methods called test
> > and test=, but you tried to call test on the class (and so you end up
> > falling through to Kernel#test).
> > Have you seen that validations take :if and :unless options ?
>
> > Fred
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Hi Frederick!

> I think you can still do
> validate :something, :if => :something+else?
I hope it could be used multiple time with different methods
> >     ruby> x = Person.newq
> >           NoMethodError: undefined method `newq'' for
Person:Class
> 
> Not sure what this is showing - you haven''t attempted to define
newq
> anywhere
Sorry It was my typing mistake.
> > test 2:
> > ....
> I ran this in irb and this worked fine.
> 
But it has not work fine, I again tested it now.
my ruby version
   ruby 1.8.7 (2010-06-23 patchlevel 299) [i686-linux]
installed using Ruby Version Manager.

For all I got why this is happening.

Great thanks for all explanations.

-- 
Regards,
-sharad

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