Raised when the arguments are wrong and there isn’t a more specific Exception class.

Ex: passing the wrong number of arguments

[1, 2, 3].first(4, 5)

raises the exception:

ArgumentError: wrong number of arguments (given 2, expected 1)

Ex: passing an argument that is not acceptable:

[1, 2, 3].first(-4)

raises the exception:

ArgumentError: negative array size
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February 12, 2009
2 thanks

Use this!

You should raise your own ArgumentError in methods to notify users of your class, if you think certain kinds of arguments aren’t acceptable.

def transfer_money(amount)
  unless amount.is_a?(Number)
    raise ArgumentError.new("Only numbers are allowed")
  end
  # ... Do the actual work
end