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Panayotis Matsinopoulos

2012-Aug-20 08:16 UTC

A rollback is not issued when dependent object before_destroy callback returns false

Hi,

I am wondering whether this is the designed behavior of ActiveRecord, when, 
to me, it is not the expected one.

I have a simple model design with an Order having many Order Items and an 
Order Item belonging to an Order. The has_many association on Order has a 
:dependent => :destroy option.
Also, the Order Item has a before_destroy function that would check the 
price of the Order Item. If the price is above 100, it returns false and 
does not allow the Order Item to be destroyed.

The classes codes has as follows:

class Order < ActiveRecord::Base
  attr_accessible :order_code
  has_many :order_items, :inverse_of => :order, :dependent => :destroy
end

class OrderItem < ActiveRecord::Base
  attr_accessible :price, :order_id

  belongs_to :order, :inverse_of => :order_items

  before_destroy :low_price

  protected

  def low_price
    if price <= 100
      puts "I have low price...I can be deleted"
      true
    else
      puts "I have high price...I cannot be deleted"
      false
    end
  end
end

The problem is that when I am issuing a destroy on an instance of an order 
that has an order item that has price > 100, then the order item is not 
deleted, but the order does. Here are the console commands and output:
> rails cLoading development environment (Rails 3.2.8)
1.9.3-p194 :001 > o = Order.new :order_code => ''first
order''
 => #<Order id: nil, order_code: "first order", created_at: nil,
updated_at: nil> 
1.9.3-p194 :002 > o.save!
   (0.1ms)  BEGIN
  SQL (0.2ms)  INSERT INTO `orders` (`created_at`, `order_code`, 
`updated_at`) VALUES (''2012-08-20 08:14:20'', ''first
order'', ''2012-08-20
08:14:20'')
   (2.0ms)  COMMIT
 => true 
1.9.3-p194 :003 > o.order_items << OrderItem.new(:price => 110)
   (0.1ms)  BEGIN
  SQL (0.3ms)  INSERT INTO `order_items` (`created_at`, `order_id`, 
`price`, `updated_at`) VALUES (''2012-08-20 08:14:31'', 5, 110,
''2012-08-20
08:14:31'')
   (0.5ms)  COMMIT
  OrderItem Load (0.3ms)  SELECT `order_items`.* FROM `order_items` WHERE 
`order_items`.`order_id` = 5
 => [#<OrderItem id: 4, order_id: 5, price: 110, created_at:
"2012-08-20
08:14:31", updated_at: "2012-08-20 08:14:31">] 
1.9.3-p194 :004 > o.destroy
   (0.2ms)  BEGIN
I have high price...I cannot be deleted
  SQL (1.0ms)  DELETE FROM `orders` WHERE `orders`.`id` = 5
   (1.8ms)  COMMIT
 => #<Order id: 5, order_code: "first order", created_at:
"2012-08-20
08:14:20", updated_at: "2012-08-20 08:14:20"> 
1.9.3-p194 :005 > 


Can somebody explain to me, why the failure of the dependent object destroy 
method does not trigger a rollback?

Thanks in advance
Panayotis

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Gintautas Šimkus

2012-Aug-21 04:34 UTC

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Re: A rollback is not issued when dependent object before_destroy callback returns false

Why would you want to return false from a callback and still destroy it? I
think you might try to squeeze two different concepts into a single method
definition: if you want to check whether or not price is lower than
something and actually USE that information somewhere else, then just
create another method "low_price?", and you can use it in
"low_price"
callback:

def low_price
  if low_price?
    # do something before the record is destroyed
  end
  true
end

def low_price?
  price <= 100
end

2012/8/20 Panayotis Matsinopoulos
<panayotis-2qElkpaxrV4pvVtuE3Kueg@public.gmane.org>
> Hi,
>
> I am wondering whether this is the designed behavior of ActiveRecord,
> when, to me, it is not the expected one.
>
> I have a simple model design with an Order having many Order Items and an
> Order Item belonging to an Order. The has_many association on Order has a
> :dependent => :destroy option.
> Also, the Order Item has a before_destroy function that would check the
> price of the Order Item. If the price is above 100, it returns false and
> does not allow the Order Item to be destroyed.
>
> The classes codes has as follows:
>
> class Order < ActiveRecord::Base
>   attr_accessible :order_code
>   has_many :order_items, :inverse_of => :order, :dependent =>
:destroy
> end
>
> class OrderItem < ActiveRecord::Base
>   attr_accessible :price, :order_id
>
>   belongs_to :order, :inverse_of => :order_items
>
>   before_destroy :low_price
>
>   protected
>
>   def low_price
>     if price <= 100
>       puts "I have low price...I can be deleted"
>       true
>     else
>       puts "I have high price...I cannot be deleted"
>       false
>     end
>   end
> end
>
> The problem is that when I am issuing a destroy on an instance of an order
> that has an order item that has price > 100, then the order item is not
> deleted, but the order does. Here are the console commands and output:
>
> > rails c
> Loading development environment (Rails 3.2.8)
> 1.9.3-p194 :001 > o = Order.new :order_code => ''first
order''
>  => #<Order id: nil, order_code: "first order", created_at:
nil,
> updated_at: nil>
> 1.9.3-p194 :002 > o.save!
>    (0.1ms)  BEGIN
>   SQL (0.2ms)  INSERT INTO `orders` (`created_at`, `order_code`,
> `updated_at`) VALUES (''2012-08-20 08:14:20'',
''first order'', ''2012-08-20
> 08:14:20'')
>    (2.0ms)  COMMIT
>  => true
> 1.9.3-p194 :003 > o.order_items << OrderItem.new(:price => 110)
>    (0.1ms)  BEGIN
>   SQL (0.3ms)  INSERT INTO `order_items` (`created_at`, `order_id`,
> `price`, `updated_at`) VALUES (''2012-08-20 08:14:31'', 5,
110, ''2012-08-20
> 08:14:31'')
>    (0.5ms)  COMMIT
>   OrderItem Load (0.3ms)  SELECT `order_items`.* FROM `order_items` WHERE
> `order_items`.`order_id` = 5
>  => [#<OrderItem id: 4, order_id: 5, price: 110, created_at:
"2012-08-20
> 08:14:31", updated_at: "2012-08-20 08:14:31">]
> 1.9.3-p194 :004 > o.destroy
>    (0.2ms)  BEGIN
> I have high price...I cannot be deleted
>   SQL (1.0ms)  DELETE FROM `orders` WHERE `orders`.`id` = 5
>    (1.8ms)  COMMIT
>  => #<Order id: 5, order_code: "first order", created_at:
"2012-08-20
> 08:14:20", updated_at: "2012-08-20 08:14:20">
> 1.9.3-p194 :005 >
>
>
> Can somebody explain to me, why the failure of the dependent object
> destroy method does not trigger a rollback?
>
> Thanks in advance
> Panayotis
>
>  --
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> "Ruby on Rails: Talk" group.
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>
>
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Gintautas Šimkus

2012-Aug-21 04:37 UTC

head link

Re: A rollback is not issued when dependent object before_destroy callback returns false

Sorry should read.

2012/8/21 Gintautas Šimkus
<dihitales-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> I think you might BE TRYING to squeeze two different concepts
>
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Panayotis Matsinopoulos

2012-Aug-21 06:16 UTC

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Re: A rollback is not issued when dependent object before_destroy callback returns false

Thanks for your answer. See my comments below

On Tuesday, August 21, 2012 7:34:34 AM UTC+3, Dihital
wrote:>
> Why would you want to return false from a callback and still destroy it? 


No. I do not want. I think you missed the point of my post. In the example 
that I have written the Order Item IS NOT CORRECTLY deleted, because it has 
high price. The PROBLEM is that the OWNING Order is deleted, when it 
shouldn''t.

Please, consider this as an example of an owner (Order in the example) 
being deleted when it shouldn''t (because of the fact that the owned
item
(Order Item in the example) is not deleted). Do not stick too much on the 
business value of the example.
There may not be much, if any.


Panayotis

 
> I think you might try to squeeze two different concepts into a single 
> method definition: if you want to check whether or not price is lower than 
> something and actually USE that information somewhere else, then just 
> create another method "low_price?", and you can use it in
"low_price"
> callback:
>
> def low_price
>   if low_price?
>     # do something before the record is destroyed
>   end
>   true
> end
>
> def low_price?
>   price <= 100
> end
>
> 2012/8/20 Panayotis Matsinopoulos
<pana...-2qElkpaxrV4pvVtuE3Kueg@public.gmane.org <javascript:>>
>
>> Hi,
>>
>> I am wondering whether this is the designed behavior of ActiveRecord, 
>> when, to me, it is not the expected one.
>>
>> I have a simple model design with an Order having many Order Items and
an
>> Order Item belonging to an Order. The has_many association on Order has
a
>> :dependent => :destroy option.
>> Also, the Order Item has a before_destroy function that would check the
>> price of the Order Item. If the price is above 100, it returns false
and
>> does not allow the Order Item to be destroyed.
>>
>> The classes codes has as follows:
>>
>> class Order < ActiveRecord::Base
>>   attr_accessible :order_code
>>   has_many :order_items, :inverse_of => :order, :dependent =>
:destroy
>> end
>>
>> class OrderItem < ActiveRecord::Base
>>   attr_accessible :price, :order_id
>>
>>   belongs_to :order, :inverse_of => :order_items
>>
>>   before_destroy :low_price
>>
>>   protected
>>
>>   def low_price
>>     if price <= 100
>>       puts "I have low price...I can be deleted"
>>       true
>>     else
>>       puts "I have high price...I cannot be deleted"
>>       false
>>     end
>>   end
>> end
>>
>> The problem is that when I am issuing a destroy on an instance of an 
>> order that has an order item that has price > 100, then the order
item is
>> not deleted, but the order does. Here are the console commands and
output:
>>
>> > rails c
>> Loading development environment (Rails 3.2.8)
>> 1.9.3-p194 :001 > o = Order.new :order_code => ''first
order''
>>  => #<Order id: nil, order_code: "first order",
created_at: nil,
>> updated_at: nil> 
>> 1.9.3-p194 :002 > o.save!
>>    (0.1ms)  BEGIN
>>   SQL (0.2ms)  INSERT INTO `orders` (`created_at`, `order_code`, 
>> `updated_at`) VALUES (''2012-08-20 08:14:20'',
''first order'', ''2012-08-20
>> 08:14:20'')
>>    (2.0ms)  COMMIT
>>  => true 
>> 1.9.3-p194 :003 > o.order_items << OrderItem.new(:price =>
110)
>>    (0.1ms)  BEGIN
>>   SQL (0.3ms)  INSERT INTO `order_items` (`created_at`, `order_id`, 
>> `price`, `updated_at`) VALUES (''2012-08-20 08:14:31'',
5, 110, ''2012-08-20
>> 08:14:31'')
>>    (0.5ms)  COMMIT
>>   OrderItem Load (0.3ms)  SELECT `order_items`.* FROM `order_items`
WHERE
>> `order_items`.`order_id` = 5
>>  => [#<OrderItem id: 4, order_id: 5, price: 110, created_at:
"2012-08-20
>> 08:14:31", updated_at: "2012-08-20 08:14:31">] 
>> 1.9.3-p194 :004 > o.destroy
>>    (0.2ms)  BEGIN
>> I have high price...I cannot be deleted
>>   SQL (1.0ms)  DELETE FROM `orders` WHERE `orders`.`id` = 5
>>    (1.8ms)  COMMIT
>>  => #<Order id: 5, order_code: "first order",
created_at: "2012-08-20
>> 08:14:20", updated_at: "2012-08-20 08:14:20"> 
>> 1.9.3-p194 :005 > 
>>
>>
>> Can somebody explain to me, why the failure of the dependent object 
>> destroy method does not trigger a rollback?
>>
>> Thanks in advance
>> Panayotis
>>
>>  -- 
>> 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
rubyonra...-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<javascript:>
>> .
>> To unsubscribe from this group, send email to 
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<javascript:>.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msg/rubyonrails-talk/-/tYWGJ6euWZQJ.
>> For more options, visit https://groups.google.com/groups/opt_out.
>>  
>>  
>>
>
>
>
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Rails - Aug 2012 - A rollback is not issued when dependent object before_destroy callback returns false

A rollback is not issued when dependent object before_destroy callback returns false

Re: A rollback is not issued when dependent object before_destroy callback returns false

Re: A rollback is not issued when dependent object before_destroy callback returns false

Re: A rollback is not issued when dependent object before_destroy callback returns false