Exceptions in Rails

exceptions.rb

How to raise an exception

#Objective: If either player's strategy is something other than "R", "P" or "S" (case-insensitive), the method should raise aRockPaperScissors::NoSuchStrategyError exception.

  1 class RockPaperScissors
  2 
  3   # Exceptions this class can raise:
  4   class NoSuchStrategyError < StandardError ; end        <<<<<<<<<<<<<<< This line defines the type of exception
				
#At appropriate point

  7     if(/R|S|P/.match(player1[1]) == nil || /R|S|P/.match(player2[1]) == nil)
  8       raise NoSuchStrategyError , "Strategy must be one of R,P,S" <<<<<< You are raising your custom expection here with custom message
  9     end

  #Notice that inside main class—> there is one more class for custom exception and it is inherited from StandardError


#Another example
#Objective:  If there's a network problem-- unfortunately, Ruby's HTTP library can raise many kinds of exceptions-- we convert any of them into a generic OracleOfBacon::NetworkError and re-raise that. 

  7 class OracleOfBacon
  8 
  9   class InvalidError < RuntimeError ; end
 10   class NetworkError < RuntimeError ; end <<<<<<<<<<<< This line defines the type of exception
 11   class InvalidKeyError < RuntimeError ; end
 12 
 36   def find_connections 37     make_uri_from_arguments
 38     begin
 39       xml = URI.parse(uri).read
 40     rescue Timeout::Error, Errno::EINVAL, Errno::ECONNRESET, EOFError,
 41       Net::HTTPBadResponse, Net::HTTPHeaderSyntaxError,
 42       Net::ProtocolError => e
 44       # convert all of these into a generic OracleOfBacon::NetworkError,
 45       #  but keep the original error message
 46       # your code here
 43       raise NetworkError          <<<<< We are raising our custom exception but since we did not specify our own message original error message is used
 47     end
 48     # your code here: create the OracleOfBacon::Response object
 49     OracleOfBacon::Response.new(xml)
 50   end