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POHow does reject_if: :all_blank for accepts_nested_attributes_for work when working with doubly nested associations?
 

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  1. POHow does reject_if: :all_blank for accepts_nested_attributes_for work when working with doubly nested associations?
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    <p>I have my model setup as below. Everything works fine except blank part records are allowed even if all part and chapter fields are blank.</p> <pre><code>class Book &lt; ActiveRecord::Base has_many :parts, inverse_of: :book accepts_nested_attributes_for :parts, reject_if: :all_blank end class Part &lt; ActiveRecord::Base belongs_to :book, inverse_of: :parts has_many :chapters, inverse_of: :part accepts_nested_attributes_for :chapters, reject_if: :all_blank end class Chapter &lt; ActiveRecord::Base belongs_to :part, inverse_of: :chapters end </code></pre> <p>Spelunking the code, <code>:all_blank</code> gets replaced with <code>proc { |attributes| attributes.all? { |key, value| key == '_destroy' || value.blank? } }</code>. So, I use that instead of <code>:all_blank</code> and add in some debugging. Looks like what is happening is the part's chapters attribute is responding to <code>blank?</code> with <code>false</code> because it is an instantiated hash object, even though all it contains is another hash that only contains blank values:</p> <pre><code>chapters_attributes: !ruby/hash:ActionController::Parameters '0': !ruby/hash:ActionController::Parameters title: '' text: '' </code></pre> <p>Is it just not meant to work this way?</p> <p>I've found a workaround:</p> <pre><code>accepts_nested_attributes_for :parts, reject_if: proc { |attributes| attributes.all? do |key, value| key == '_destroy' || value.blank? || (value.is_a?(Hash) &amp;&amp; value.all? { |key2, value2| value2.all? { |key3, value3| key3 == '_destroy' || value3.blank? } }) end } </code></pre> <p>But I was hoping I was missing a better way to handle this.</p> <hr> <p><strong>Update 1:</strong> I tried redefining <code>blank?</code> for <code>Hash</code> but that causes probs.</p> <pre><code>class Hash def blank? :empty? || all? { |k,v| v.blank? } end end </code></pre> <hr> <p><strong>Update 2:</strong> This makes <code>:all_blank</code> work as I was expecting it to, but it is ugly and not well-tested.</p> <pre><code>module ActiveRecord::NestedAttributes::ClassMethods REJECT_ALL_BLANK_PROC = proc { |attributes| attributes.all? { |k, v| k == '_destroy' || v.valueless? } } end class Object alias_method :valueless?, :blank? end class Hash def valueless? blank? || all? { |k, v| v.valueless? } end end </code></pre> <hr> <p><strong>Update 3:</strong> Doh! Update 1 had a typo in it. This version does seem to work. </p> <pre><code>class Hash def blank? empty? || all? { |k,v| v.blank? } end end </code></pre> <p>Does this have too much potential for unintended consequences to be a viable option? If this is a good option, where in my app should this code live?</p>
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