Exceptions

Ruby has exceptions [1]. Similar to the finally in Java, Ruby has an ensure which will always execute regardless of whether an exception is raised [1]. The try block, which is begin and end in Ruby, can have multiple catch blocks, which are rescue blocks in Ruby.

For example:

rescue.rb

begin
  "Hello".even?                             # String does not have even? method
rescue TypeError
  puts "Wrong type"                         # First catch/rescue
rescue NoMethodError
  puts "No method even for String Hello"    # Second catch/rescue
ensure
  puts "Finally, String is not even or odd" # Always execute
end

Source code: https://github.com/yc015/Ruby-Inspect/blob/main/src/rescue.rb

The codes above will print:

No method even for String Hello
Finally, String is not even or odd

We can create our own exceptions. For example:

custom_exceptions.rb

class MyCustomError < StandardError
  attr_reader :reason
  def initialize(reason)
    @reason = reason
  end
end

raise MyCustomError.new("My Error!")

Source code: https://github.com/yc015/Ruby-Inspect/blob/main/src/custom_exceptions.rb

The codes above will raise MyCustomError.

Reference:
[1] https://www.tutorialspoint.com/ruby/ruby_exceptions.htm Ruby Exceptions - Tutorialspoint