Private method in Ruby

In Ruby, private methods are defined using the keyword private. Private methods can only be called from within the class in which they are defined and cannot be called from outside the class.

Here is an example of a class with a private method in Ruby:

class Car
  def initialize(make, model)
    @make = make
    @model = model
  end
  
  def start_engine
    # Call private method from within class
    ignite_engine
    puts "Engine started"
  end
  
  private
  
  def ignite_engine
    puts "Igniting engine for #{@make} #{@model}"
  end
end
car = Car.new("Toyota", "Camry")

car.start_engine # Output: Igniting engine for Toyota Camry

                 #         Engine started
# Try to call private method from outside class

car.ignite_engine # Output: NoMethodError: private method ignite_engine' called for #

In this example, the ignite_engine method is defined as a private method using the keyword private. This method is only called from within the start_engine method which is defined as a public method.

When we create a new instance of the Car class and call the start_engine method, the private method ignite_engine is called via the start_engine method.

However, when we try to call the private method ignite_engine from outside the class using the car.ignite_engine syntax, we get a NoMethodError` because private methods can only be called from within the class in which they are defined.