Question

Is there something built-in with Ruby to determine if a string is a reserved word? Something like "next".is_keyword??

Answer 1

The only way I can think of is loading an array with all the keywords you know about.

class String
  def is_keyword?
    %w{__FILE__ __LINE__ alias and begin BEGIN break case class def defined? do else elsif end END ensure false for if in module next nil not or redo rescue retry return self super then true undef unless until when while yield}.include? self
  end
end
"foobar".is_keyword? # => false
"for".is_keyword? # => true

For reference:

• I know this isn’t a built-in way, it’s just the only way I could think of. Don’t downvote me for it.
• The list I included is that of true keywords. public, protected and friends aren’t really keywords, just the names of important methods which are called during the creation of modules or classes. You can think of it as elements of the Ruby DSL.