Raise custom Exception with arguments

Question

I\'m defining a custom Exception on a model in rails as kind of a wrapper Exception: (begin[code]rescue[raise custom exception]end)

When I raise the Exc

Answer 1

Simple pattern for custom errors with additional information

If the extra information you're looking to pass is simply a type with a message, this works well:

# define custom error class
class MyCustomError < StandardError; end

# raise error with extra information
raise MyCustomError, 'Extra Information'

The result (in IRB):

Traceback (most recent call last):
        2: from (irb):22
        1: from (irb):22:in `rescue in irb_binding'
MyCustomError (Extra Information)

Example in a class

The pattern below has become exceptionally useful for me (pun intended). It's clean, can be easily modularized, and the errors are expressive. Within my class I define new errors that inherit from StandardError, and I raise them with messages (for example, the object associated with the error).

Here's a simple example, similar to OP's original question, that raises a custom error within a class and captures the method name in the error message:

class MyUser
  # class errors
  class MyUserInitializationError < StandardError; end

  # instance methods
  def simulate_failure
    raise MyUserInitializationError, "method failed: #{__method__}"
  end
end

# example usage: 
MyUser.new.simulate_failure

# => MyUser::MyUserInitializationError (method failed: simulate_failure)