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POMerging the Associations of a Parent, its Children and it's Childrens' Children with Rails3
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copied!<p>I have a model <code>Foo</code>. <code>Foo</code> has many children of type <code>FooChild</code>. <code>FooChild</code> has many <code>FooChildChild</code>. <code>Foo</code>, <code>FooChild</code> and <code>FooChildChild</code> all have and belong to many <code>Bar</code>. I want to create a method or scope on <code>Foo</code> that will return all of the <code>Bar</code> associated with it and it's child associations. I currently have something like the following on the <code>Foo</code> model.</p> <pre><code>def foo_child_bars b = [] self.foo_childs.includes(:bar).collect{|fc| b += fc.bar} b.uniq end def foo_child_child_bars b = [] self.foo_childs.includes(:foo_child_childs).collect{|fcc| b += fcc.bar} b.uniq end def all_bars (self.bars + self.foo_child_bars + self.foo_child_child_bars).uniq end </code></pre> <p>So now I can call <code>@foo.all_bars</code> and this works and I don't get duplicates because of the <code>.uniq</code> method.</p> <p>I imagine that this sort of operation is rather inefficient due to the fact that I'm performing three separate queries. Ideally I'd like to do a single query with a <code>UNION</code> or something so that the database does the heavy lifting of ensuring only unique records are returned and I'm doing as few queries as possible.</p> <p>I'm also curious if there is a way to use <code>includes()</code> on a nested association such that <code>foo_child_child_bars()</code> could include the <code>:bars</code> which are associated with all of the <code>:foo_child_childs</code> which are being included.</p> <p><code>Bar</code> in this reduction represents a table <code>'images'</code> which has <a href="https://github.com/jnicklas/carrierwave" rel="nofollow">CarrierWave</a> set up on the <code>Image</code> model for managing uploaded images. I'm almost positive that there is a gem out there that would probably simplify this whole thing, but I'd rather just make what I have work and tackle that gem implementation later as it will likely involve a lot of complicated table migrations and refactoring.</p>

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