From: Intransition <transfire@...>
Date: 2013-01-06T18:31:22+09:00
Subject: Re: respond_to_missing?

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On Saturday, January 5, 2013 4:00:02 PM UTC-5, Jan E. wrote:
>
> How is that contradictory? Are you sure you got the return values of 
> respond_to_missing? right? Because I guess you want to return *true* for 
> :to_ary? 
>
> respond_to? first checks if the method is actually, physically there. If 
> that's not the case, it checks for respond_to_missing? 
>
> In your case both checks return "false", so you end up with "false" just 
> like you should. 
>
>
Yes, that is what it should do. But notice #flatten doesn't seem to notice 
that it returns false. It still calls #to_ary on it,

    class Baz
      def method_missing(s); s; end

      def respond_to_missing?(s, x)
        return false if s == :to_ary
        true
      end
    end


    [Baz.new].flatten
    => in `flatten': can't convert Baz to Array (Baz#to_ary gives Symbol) (TypeError)


Even though it appears to work fine if one overrides #respond_to? directly. 

    class Baz

      def method_missing(s); s; end

      def respond_to?(s, x)
        super unless s == :to_ary
      end
    end
 
    [Baz.new].flatten => [#<Baz:0x007f8d3115c7d0>]


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<br>On Saturday, January 5, 2013 4:00:02 PM UTC-5, Jan E. wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">How is that contradictory? Are you sure you got the return values of 
<br>respond_to_missing? right? Because I guess you want to return *true* for 
<br>:to_ary?
<br>
<br>respond_to? first checks if the method is actually, physically there. If 
<br>that's not the case, it checks for respond_to_missing?
<br>
<br>In your case both checks return "false", so you end up with "false" just 
<br>like you should.
<br>
<br></blockquote><div><br>Yes, that is what it should do. But notice #flatten doesn't seem to notice that it returns false. It still calls #to_ary on it,<br><br><pre><span style="font-family: courier new,monospace;">    class Baz
      def method_missing(s); s; end

      def respond_to_missing?(s, x)
        return false if s == :to_ary
        true
      end
    end
</span></pre><span style="font-family: courier new,monospace;"><br></span><pre><span style="font-family: courier new,monospace;">    [Baz.new].flatten
    =&gt; in `flatten': can't convert Baz to Array (Baz#to_ary gives Symbol) (TypeError)</span></pre><br>Even though it appears to work fine if one overrides #respond_to? directly. <br></div><span style="font-family: courier new,monospace;"><br>&nbsp;&nbsp;&nbsp; class Baz<br></span><pre><span style="font-family: courier new,monospace;">      def method_missing(s); s; end<br><br></span></pre><span style="font-family: courier new,monospace;">&nbsp;&nbsp; &nbsp;&nbsp; def respond_to?(s, x)<br>&nbsp; &nbsp; &nbsp;&nbsp;&nbsp; super unless s == :to_ary<br>&nbsp; &nbsp;&nbsp;&nbsp; end<br>&nbsp;&nbsp;&nbsp; end<br>&nbsp;<br>&nbsp;&nbsp;&nbsp; [Baz.new].flatten
=&gt; [#&lt;Baz:0x007f8d3115c7d0&gt;]<br><br></span>
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