Weird stuff with hashes

Ok, so this isn’t really weird stuff, I don’t think. But maybe people don’t know about it so I thought I would post. Hashes dup string keys When you assign a string key to a hash, the hash copies the string and freezes it. Here is an example: >> x = 'string' => "string" >> y = {} => {} >> y[x] = :value => :value >> { x => y.keys.first } => {"string"=>"string"} >> { x.object_id => y.keys.first.object_id } => {70157126548460=>70157126526760} # object ids are different >> { x.frozen? => y.keys.first.frozen? } => {false=>true} # frozen value is different You can prevent the string from being duped by freezing the string before putting it in the hash: