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copied!<p>There's not a built in function to say if a string is effectively an integer, but you can easily make your own:</p> <pre><code>class String def int Integer(self) rescue nil end end </code></pre> <p>This works because the Kernel method <code>Integer()</code> throws an error if the string can't be converted to an integer, and the inline <code>rescue nil</code> turns that error into a nil.</p> <pre><code>Integer("1") -> 1 Integer("1x") -> nil Integer("x") -> nil </code></pre> <p>and thus:</p> <pre><code>"1".int -> 1 (which in boolean terms is `true`) "1x".int -> nil "x".int -> nil </code></pre> <p>You could alter the function to return <code>true</code> in the true cases, instead of the integer itself, but if you're testing the string to see if it's an integer, chances are you want to use that integer for something! I very commonly do stuff like this:</p> <pre><code>if i = str.int # do stuff with the integer i else # error handling for non-integer strings end </code></pre> <p>Although if the assignment in a test position offends you, you can always do it like this:</p> <pre><code>i = str.int if i # do stuff with the integer i else # error handling for non-integer strings end </code></pre> <p>Either way, this method only does the conversion once, which if you have to do a lot of these, may be a significant speed advantage.</p> <p>[Changed function name from <code>int?</code> to <code>int</code> to avoid implying it should return just true/false.]</p>

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