Rails - May 2012 - Updating attribute on dependent of many-to-on association

All,

I posted this over on comp.lang.ruby, but realized I should probably
keep Rails questions to this group, so soory for the cross-post.

I have a rails app with a Transaction class that has_many :entries.
Each Transaction has many entries, and those with the debit attribute
true are debits, false are credits.  It starts like this.

class Transaction < ActiveRecord::Base
  has_many :entries
  has_many :debits, :class_name => ''Entry'', :conditions
=> {:debit =>
true}
  has_many :credits, :class_name => ''Entry'', :conditions
=> {:debit =>
false}
end

I want to be able to complete an Transaction if there is exactly one
Entry that has its amount set to nil.  I want to set that amount to a
debit or credit of the proper amount to make the Transaction balance.

Sounded easy to me, but I am having trouble with my balance! method.
The relevant part of it is:

  def balance!
    ...
    if num_nils == 1
      # Set the sole nil entry to amount needed to balance Transaction
      plug = debit_total - credit_total
      entries.where(:amount => nil).each do |e|
        e.amount = plug.abs
        e.debit = (plug < 0)
        e.save
      end
    end

The problem is that when I finish this, the entries associated with my
Transaction are not affected.  I appears to make a copy, change it,
and
leave the Entry associated with my Transaction with a nil amount.

What am I missing?

Thanks,

Dan Doherty

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On 25 May 2012 04:43, ddoherty03
<ddoherty03-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> All,
>
> I posted this over on comp.lang.ruby, but realized I should probably
> keep Rails questions to this group, so soory for the cross-post.
>
> I have a rails app with a Transaction class that has_many :entries.
> Each Transaction has many entries, and those with the debit attribute
> true are debits, false are credits.  It starts like this.
>
> class Transaction < ActiveRecord::Base
>  has_many :entries
>  has_many :debits, :class_name => ''Entry'', :conditions
=> {:debit =>
> true}
>  has_many :credits, :class_name => ''Entry'',
:conditions => {:debit =>
> false}
> end
>
> I want to be able to complete an Transaction if there is exactly one
> Entry that has its amount set to nil.  I want to set that amount to a
> debit or credit of the proper amount to make the Transaction balance.
>
> Sounded easy to me, but I am having trouble with my balance! method.
> The relevant part of it is:
>
>  def balance!
>    ...
>    if num_nils == 1
>      # Set the sole nil entry to amount needed to balance Transaction
>      plug = debit_total - credit_total
>      entries.where(:amount => nil).each do |e|
>        e.amount = plug.abs
>        e.debit = (plug < 0)
>        e.save
>      end
>    end
>
> The problem is that when I finish this, the entries associated with my
> Transaction are not affected.  I appears to make a copy, change it,
> and
> leave the Entry associated with my Transaction with a nil amount.
>
> What am I missing?
The first thing to determine is which bit is failing.  Is the code in
the each loop actually running?  Does the save work (check the return
code from save)?  Have a look at the Rails Guide on debugging for help
on how to debug the code.

Not directly related to the question but I find it hard to believe
that the way you are going about this is ideal.  I suggest it would be
better not do directly differentiate between debits and credits as you
are, but just to have positive or negative transaction values.
However as I know little about what you are trying to achieve this may
be incorrect.

Also I suspect that transaction may be a reserved word in rails, so
this might give you problems.

Colin
>
> Thanks,
>
> Dan Doherty
>
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Colin,

Thanks for taking a look at this.  After a good night''s sleep, I came
back
to this, and the problem appears to be
 that  I need to self.reload after the loop.  I believe this is because of 
the nature of the association, which depend on whether 
debit is true or false, and I believe need re-reading from the db after the 
e.save.

For anyone interested, here is what fixed it:

  if num_nils == 1 
      # Set the sole nil entry to amount needed to balance Transaction 
      plug = debit_total - credit_total 
      entries.where(:amount => nil).each do |e| 
        e.amount = plug.abs 
        e.debit = (plug < 0) 
        e.save 
      end
      reload    # <= New line
    end 

Th

On Friday, May 25, 2012 2:35:08 AM UTC-5, Colin Law
wrote:
>
>
> > All, 
> > 
> > I posted this over on comp.lang.ruby, but realized I should probably 
> > keep Rails questions to this group, so soory for the cross-post. 
> > 
> > I have a rails app with a Transaction class that has_many :entries. 
> > Each Transaction has many entries, and those with the debit attribute 
> > true are debits, false are credits.  It starts like this. 
> > 
> > class Transaction < ActiveRecord::Base 
> >  has_many :entries 
> >  has_many :debits, :class_name => ''Entry'',
:conditions => {:debit =>
> > true} 
> >  has_many :credits, :class_name => ''Entry'',
:conditions => {:debit =>
> > false} 
> > end 
> > 
> > I want to be able to complete an Transaction if there is exactly one 
> > Entry that has its amount set to nil.  I want to set that amount to a 
> > debit or credit of the proper amount to make the Transaction balance. 
> > 
> > Sounded easy to me, but I am having trouble with my balance! method. 
> > The relevant part of it is: 
> > 
> >  def balance! 
> >    ... 
> >    if num_nils == 1 
> >      # Set the sole nil entry to amount needed to balance Transaction 
> >      plug = debit_total - credit_total 
> >      entries.where(:amount => nil).each do |e| 
> >        e.amount = plug.abs 
> >        e.debit = (plug < 0) 
> >        e.save 
> >      end 
> >    end 
> > 
> > The problem is that when I finish this, the entries associated with my
> > Transaction are not affected.  I appears to make a copy, change it, 
> > and 
> > leave the Entry associated with my Transaction with a nil amount. 
> > 
> > What am I missing? 
>
> The first thing to determine is which bit is failing.  Is the code in 
> the each loop actually running?  Does the save work (check the return 
> code from save)?  Have a look at the Rails Guide on debugging for help 
> on how to debug the code. 
>
> Not directly related to the question but I find it hard to believe 
> that the way you are going about this is ideal.  I suggest it would be 
> better not do directly differentiate between debits and credits as you 
> are, but just to have positive or negative transaction values. 
> However as I know little about what you are trying to achieve this may 
> be incorrect. 
>
> Also I suspect that transaction may be a reserved word in rails, so 
> this might give you problems. 
>
> Colin 
>
> > 
> > Thanks, 
> > 
> > Dan Doherty 
> > 
> > -- 
> > You received this message because you are subscribed to the Google 
> Groups "Ruby on Rails: Talk" group. 
> > To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> > To unsubscribe from this group, send email to 
>
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
> > For more options, visit this group at 
> http://groups.google.com/group/rubyonrails-talk?hl=en. 
> > 
>
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