01 - raising an exception.rb

O Reilly Ruby Cookbook source code

def raise_exception
  puts 'I am before the raise.'
  raise 'An error has occurred.'
  puts 'I am after the raise.'
end

raise_exception
# I am before the raise.
# RuntimeError: An error has occurred
#---
def inverse(x)
  raise "Argument is not numeric" unless x.is_a? Numeric
  1.0 / x
end
#---
inverse(2)                               # => 0.5
#---
inverse('not a number')
# RuntimeError: Argument is not numeric
#---
ObjectSpace.each_object(Class) do |x| 
  puts x if x.ancestors.member? Exception
end
#---
ObjectSpace.each_object(Class) { |x| puts x if x.name =~ /Error$/ }
# SystemStackError
# LocalJumpError
# EOFError
# IOError
# RegexpError
# ...
#---
def inverse(x)
  raise ArgumentError, 'Argument is not numeric' unless x.is_a? Numeric
  1.0 / x
end
#---
class NotInvertibleError < StandardError
end
#---
def inverse(x)
  raise NotInvertibleError, 'Argument is not numeric' unless x.is_a? Numeric
  1.0 / x
end

inverse('not a number')
# NotInvertibleError: Argument is not numeric
#---