Question

When you call a method that does not exist on an object a NoMethodError will be raised i.e.

Object.new.foo

will output:

NoMethodError: undefined method `foo’ for #

while

nil.foo

will output:

NoMethodError: undefined method `foo’ for nil:NilClass

I want to copy this behaviour when raising an exception of my own, i.e.

foo = Object.new
raise StandardError, "#{foo} triggered an error"

which will output:

StandardError: #<Object:0xbf37748> triggered an error

which is exatly what I want.

Unfortunately

foo = nil
raise StandardError, "#{foo} triggered an error"

will output

StandardError: triggered an error

which is probably because nil.to_s is "". How do I get nil:NillClass as output?

Answer 1

raise StandardError, "#{foo.inspect}:#{foo.class} triggered an error"

Edit. You seem to want nil to behave differently. So prepare a different method just for using in your raise statement.

class Object; def my_inspect; inspect end end
class NilClass; def my_inspect; "#{inspect}:#{self.class}" end end

raise StandardError, "#{foo.my_inspect} triggered an error"