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POWhy does this 'validate' method raise an ArgumentError?
 

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  1. POWhy does this 'validate' method raise an ArgumentError?
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    <p>Folks,</p> <p>I can't get <code>validates_with</code> in my (helloworld-y) rails app to work. Read through "callbacks and validators" section of the original <a href="http://guides.rubyonrails.org/active_record_validations_callbacks.html#validates_with" rel="nofollow">RoR guides site</a> and searched stackoverflow, found nothing.</p> <p>Here's the stripped-down version of code I got after removing everything that can fail.</p> <pre><code>class BareBonesValidator &lt; ActiveModel::Validator def validate # irrelevant logic. whatever i put here raises the same error - even no logic at all end end class Unvalidable &lt; ActiveRecord::Base validates_with BareBonesValidator end </code></pre> <p>Looks like textbook example, right? They have the very similar snippet on <a href="http://guides.rubyonrails.org/active_record_validations_callbacks.html#validates_with" rel="nofollow">RoR guides</a>. Then we go to the <code>rails console</code> and get an ArgumentError while validating new record:</p> <pre><code>ruby-1.9.2-p180 :022 &gt; o = Unvalidable.new =&gt; #&lt;Unvalidable id: nil, name: nil, created_at: nil, updated_at: nil&gt; ruby-1.9.2-p180 :023 &gt; o.save ArgumentError: wrong number of arguments (1 for 0) from /Users/ujn/src/yes/app/models/unvalidable.rb:3:in `validate' from /Users/ujn/.rvm/gems/ruby-1.9.2-p180@wimmie/gems/activesupport-3.0.7/lib/active_support/callbacks.rb:315:in `_callback_before_43' </code></pre> <p>I know I'm missing something, but what?</p> <p>(NB: To avoid putting <code>BareBonesValidator</code> into separate file I left it atop <code>model/unvalidable.rb</code>).</p>
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    1. COWelcome! I see that you are new to SO. Note that the way SO works is to accept and upvote the answers you get, if you find that the answer solved your problem. Read the FAQ too.
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    2. CO@zabba — thank you. Now maybe you can help me with one SO-etiquette related question.... See, Wiltrant's answer was more concise, but yours contaned explanation of `ArgumentError` which would be useful for future readers. So I accepted his answer, then copypasted some info from yours into his. Is it OK?)
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    3. COUsually you should not edit answers. And not for the purpose of creating one "complete" answer from the other answers. I suppose editing answers to only fix typo/grammar is the correct thing to do. For everything else, you should leave a comment at that answer. One thing that @Michaël Witrant did mention which I forgot to, is how to "set an error" in the `validate` method.
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