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POHow do I make get attr_accessor_with_default work with a collection?
 

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  1. POHow do I make get attr_accessor_with_default work with a collection?
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    <p>I want to give one of my models an attribute accessor that defaults to an array of eight zeros. This is the first syntax I tried:</p> <pre><code>attr_accessor_with_default:weekly_magnitude_list, [0,0,0,0,0,0,0,0] </code></pre> <p>The above didn't do what I expected because all instances of the model end up sharing the same Array object. The blog (<a href="http://barelyenough.org/blog/2007/09/things-to-be-suspicious-of-attr_accessor_with_default-with-a-collection/" rel="nofollow noreferrer">http://barelyenough.org/blog/2007/09/things-to-be-suspicious-of-attr_accessor_with_default-with-a-collection/</a>) that clued me into that suggested a different syntax, basically wrapping the default value in a block.</p> <pre><code>attr_accessor_with_default(:weekly_magnitude_list) {[0,0,0,0,0,0,0,0]} </code></pre> <p>That doesn't work (for me, in Rails 3). Any time I call the accessor, I seem to be getting a completely new Array object. That effectively means I can't write to it. </p> <p>Does anybody know the correct way to do this?</p> <p>For your pleasure, I've included the output of a simple test demonstrating this:</p> <pre><code>class Container attr_accessor_with_default :naive_collection, [0,0] attr_accessor_with_default(:block_collection) {[0,0]} end &gt; c = Container.new =&gt; #&lt;Container:0x7f3610f717a8&gt; &gt; c.naive_collection[0] = "foo" =&gt; "foo" &gt; Container.new.naive_collection =&gt; ["foo", 0] # expected [0,0] &gt; c.block_collection[0] = "foo" =&gt; "foo" &gt; c.block_collection =&gt; [0, 0] # expected ["foo", 0] </code></pre>
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