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POWhat is the shortest/most idiomatic way of determining whether a variable is any one of a list of values?
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copied!<p>This seems a ridiculously simple question to be asking, but what's the shortest/most idiomatic way of rewriting this in Ruby?</p> <pre><code>if variable == :a or variable == :b or variable == :c or variable == :d # etc. </code></pre> <p>I saw this solution:</p> <pre><code>if [:a, :b, :c, :d].include? variable </code></pre> <p>but this isn't always functionally equivalent - I believe <code>Array#include?</code> actually looks to see if the variable object is contained in the list; it doesn't take into account that the object may implement its own equality test with <code>def ==(other)</code>.</p> <p>As observed by helpful commentators below, that explanation isn't correct. <code>include?</code> does use <code>==</code> but it uses the <code>==</code> method of the items in the array. In my example, it's the symbols, rather than the <code>==</code> method of the variable. That explains why it's not equivalent to my first code example.</p> <p>(Take, for example, Rails' <code>Mime::Type</code> implementation: <code>request.format == :html</code> may return true, but <code>[:html].include?(request.format)</code> will return false, as <code>request.format</code> is an instance of Mime::Type, not a symbol.)</p> <p>The best I have so far is:</p> <pre><code>if [:a, :b, :c, :d].select {|f| variable == f}.any? </code></pre> <p>but it seems somewhat cumbersome to me. Does anyone have better suggestions?</p>

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