From: Josh Cheek <josh.cheek@...>
Date: 2013-02-20T12:47:10+09:00
Subject: Re: ActiveRecord callback chain exception?

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On Tue, Feb 19, 2013 at 7:21 PM, Craayzie As a fox <lists@ruby-forum.com>wrote:

> I'm creating an ActiveRecord object A and want to update object B during
> the process even if the creation of object A is rolled back due to a
> before_create callback returning false.
>
> Is there a way for me to do this?
>
> It seems that once you're in the ActiveRecord callback chain your DB
> updates will be rolled back unless the entire callback chain returns
> true.
>
> Another way to look at this: I need to track all ActiveRecord "create"
> attempts but it seems that I'm unable to use callbacks or observers to
> do this since both are referenced within the ActiveRecord callback
> chain.
>
> How would you go about doing this?
>
> Thanks for the help!
>
> --
> Posted via http://www.ruby-forum.com/.
>
>
You could use a database level trigger, e.g.
http://www.postgresql.org/docs/9.1/static/sql-createtrigger.html

I don't know your needs, but I generally try to avoid things like this,
because it means you can't create the A without the B being created. It is
better to have this available, but not mandatory (don't couple your future
use to your current use).

So I'd maybe make some method whose job is to create the record and record
the attempt whether it passes or fails (IOW, do not use the callback).

Something like this:


require 'active_record'
ActiveRecord::Base.establish_connection adapter: 'sqlite3', database:
':memory:'
ActiveRecord::Schema.define do
  self.verbose = false
  create_table(:as) { |t| t.string :s }
  create_table :bs do |t|
    t.string  :initialization_attributes
    t.boolean :success
  end
end

class A < ActiveRecord::Base
  validates :s, format: { with: /x/ }
end

class B < ActiveRecord::Base
  def self.record(attributes)
    A.new attributes do |obj|
      create! initialization_attributes: attributes, success: obj.save
    end
  end

  serialize :initialization_attributes
end

B.record(s: 'x').persisted? # => true
B.record(s: 'y').persisted? # => false

A.count # => 1
B.count # => 2

x, y = B.all
x # => #<B id: 1, initialization_attributes: {:s=>"x"}, success: true>
y # => #<B id: 2, initialization_attributes: {:s=>"y"}, success: false>


The downside is you lose the ability to do things like
c.as.build(attributes)

-Josh

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On Tue, Feb 19, 2013 at 7:21 PM, Craayzie As a fox <span dir=3D"ltr">&lt;<a=
 href=3D"mailto:lists@ruby-forum.com" target=3D"_blank">lists@ruby-forum.co=
m</a>&gt;</span> wrote:<br><div class=3D"gmail_quote"><blockquote class=3D"=
gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-=
left:1ex">
I&#39;m creating an ActiveRecord object A and want to update object B durin=
g<br>
the process even if the creation of object A is rolled back due to a<br>
before_create callback returning false.<br>
<br>
Is there a way for me to do this?<br>
<br>
It seems that once you&#39;re in the ActiveRecord callback chain your DB<br=
>
updates will be rolled back unless the entire callback chain returns<br>
true.<br>
<br>
Another way to look at this: I need to track all ActiveRecord &quot;create&=
quot;<br>
attempts but it seems that I&#39;m unable to use callbacks or observers to<=
br>
do this since both are referenced within the ActiveRecord callback<br>
chain.<br>
<br>
How would you go about doing this?<br>
<br>
Thanks for the help!<br>
<span class=3D"HOEnZb"><font color=3D"#888888"><br>
--<br>
Posted via <a href=3D"http://www.ruby-forum.com/" target=3D"_blank">http://=
www.ruby-forum.com/</a>.<br>
<br>
</font></span></blockquote></div><div><br></div>You could use a database le=
vel trigger, e.g.=A0<a href=3D"http://www.postgresql.org/docs/9.1/static/sq=
l-createtrigger.html">http://www.postgresql.org/docs/9.1/static/sql-createt=
rigger.html</a><div>
<br></div><div>I don&#39;t know your needs, but I generally try to avoid th=
ings like this, because it means you can&#39;t create the A without the B b=
eing created. It is better to have this available, but not mandatory (don&#=
39;t couple your future use to your current use).</div>
<div><br><div>So I&#39;d maybe make some method whose job is to create the =
record and record the attempt whether it passes or fails (IOW, do not use t=
he callback).</div></div><div><br></div><div>Something like this:</div>
<div><br></div><div><br></div><div><div>require &#39;active_record&#39;</di=
v><div>ActiveRecord::Base.establish_connection adapter: &#39;sqlite3&#39;, =
database: &#39;:memory:&#39;</div><div>ActiveRecord::Schema.define do</div>
<div>=A0 self.verbose =3D false</div><div>=A0 create_table(:as) { |t| t.str=
ing :s } =A0</div><div>=A0 create_table :bs do |t|</div><div>=A0 =A0 t.stri=
ng =A0:initialization_attributes</div><div>=A0 =A0 t.boolean :success</div>=
<div>=A0 end</div>
<div>end</div><div><br></div><div>class A &lt; ActiveRecord::Base</div><div=
>=A0 validates :s, format: { with: /x/ }</div><div>end</div><div><br></div>=
<div>class B &lt; ActiveRecord::Base</div><div>=A0 def self.record(attribut=
es)</div>
<div>=A0 =A0 A.new attributes do |obj|</div><div>=A0 =A0 =A0 create! initia=
lization_attributes: attributes, success: obj.save</div><div>=A0 =A0 end</d=
iv><div>=A0 end</div><div>=A0=A0</div><div>=A0 serialize :initialization_at=
tributes</div><div>
end</div><div><br></div><div>B.record(s: &#39;x&#39;).persisted? # =3D&gt; =
true</div><div>B.record(s: &#39;y&#39;).persisted? # =3D&gt; false</div><di=
v><br></div><div>A.count # =3D&gt; 1</div><div>B.count # =3D&gt; 2</div><di=
v><br>
</div><div>x, y =3D B.all</div><div>x # =3D&gt; #&lt;B id: 1, initializatio=
n_attributes: {:s=3D&gt;&quot;x&quot;}, success: true&gt;</div><div>y # =3D=
&gt; #&lt;B id: 2, initialization_attributes: {:s=3D&gt;&quot;y&quot;}, suc=
cess: false&gt;</div>
</div><div><br></div><div><br></div><div>The downside is you lose the abili=
ty to do things like c.as.build(attributes)</div><div><br></div><div>-Josh<=
/div>

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