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POActiveRecord has_many association doesn't call after_destroy when setting a collection
 

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    <p>3 models: User, Movie, Like</p> <pre><code>User has_many :likes User has_many :movies, through: :likes </code></pre> <p>This code:</p> <pre><code>user.movies = [ m1, m2, m3 ] </code></pre> <p>calls <code>Like#after_create</code> for the new <code>Like</code> records that relate user and m1/m2/m3. Then, this code:</p> <pre><code>user.movies = [ m3, m4 ] </code></pre> <p>doesn't call <code>Like#after_destroy</code> for the <code>Like</code> records that relate user to m1/m2, but does call <code>Like#after_create</code> for the new relationship with m4.</p> <p>The <code>movies</code> collection could be set manually or with a form that has <code>user[movie_ids]</code> checkboxes, and then</p> <pre><code>user.update_attributes(params[:user]) </code></pre> <ol> <li>What is the right Rails approach for setting a collection?</li> <li>How do I force it to call after_destroy?</li> </ol> <h1>Update:</h1> <p>As @jdoe cited from the docs, it's not achievable when assigning new collection or when deleting from a collection (<code>user.movies.delete(m1)</code>). The only way is to use <code>before_remove</code>/<code>after_remove</code> callbacks on the user model (and in case of a polymorphic relationship -- any other model), with the <code>has_many</code> definition:</p> <pre><code>has_many :movies, through: :likes, before_remove: :before_like_destroy, after_remove: after_like_destroy def before_like_destroy(movie) like = self.likes.where(movie_id: movie) # trigger the after_destroy on like like.trigger_before_destroy # to be implemented on like, should call what the original callbacks contained end def after_like_destroy(movie) # no way to get Like object here because it was already removed, need to remember it on the before_destroy somehow end </code></pre> <p>Can't understand the logic behind it. It makes callbacks on relationship models totally useless. If something happened on <code>after_create</code> it can't be undone in <code>after_destroy</code>, and since it's better practice to have after and before logic together and not separately, it makes all callbacks useless.</p> <p>Think I'm gonna write a gem that does that automagically.</p>
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