Add a new method by add method to Class


class String
  def last(n)
    self[-n, n]
  end
end
p "Here's a string.".last(7)               # => "string."

1.	Creating and Calling a Method
2.	A simple definition for a method named hello, created with the keywords def and end
3.	define methods that have arguments
4.	You can a function with or without parenthesis
5.	Call a function for a parameter with or without parenthesis
6.	You can call another function based on the return from this funtion call
7.	method with ?
8.	Define a method to convert Cartesian (x,y) coordinates to Polar

Add a new method by add method to Class : Method Creation « Method « Ruby