Ruby setter & getter methods are similar to properties used in .net. They are used to access the instance variables of a class outside the class using the object of the class. By default instance variables are only accessible inside the instance methods, but setter & getter allow us to access them outside the class directly with the use of object of the class.

Setter & getter can be accessed in the following ways in ruby

1) By defining the setter & getter methods which would be called using the object of the class.

class Vehicle
  def initialize(name, company_name, color)
    @name = name
    @company_name = company_name
    @color = color
  end

  def color=(new_color)
      @color = new_color
  end

  def color
    @color
  end  
end

vehicle = Vehicle.new("eon","Hyundai","white")
vehicle.color = "Blue"
p "New color for eon is = " + vehicle.color

After Execution we get :

taran@taran-System-Product-Name:~/Documents/ruby_prgms$ ruby Vehicle.rb
"New color for vehicle is = Blue"

2) By using the attr_reader & attr_writer methods given by ruby which automatically creates the setter & getter method for us

class VehicleNew
  attr_reader :color
  attr_writer :color
  def initialize(name, company_name, color)
    @name = name
    @company_name = company_name
    @color = color
  end
end

vehicle = VehicleNew.new("baleno","Maruti","white")
vehicle.color = "Red"
p "New color for baleno is = " + vehicle.color

After Execution we get :

taran@taran-System-Product-Name:~/Documents/ruby_prgms$ ruby VehicleNew.rb
"New color for vehicle is = Red"

3) By using attr_accessor which provides both setter & getter method automatically. It is equivalent of using attr_reader & attr_writer

class VehicleNew1
  attr_accessor :color
  def initialize(name, company_name, color)
    @name = name
    @company_name = company_name
    @color = color
  end
end

vehicle = VehicleNew1.new("XUV 500","Mahindra","white")
vehicle.color = "Black"
p "New color for XUV 500 is = " + vehicle.color

After Execution we get :

taran@taran-System-Product-Name:~/Documents/ruby_prgms$ ruby VehicleNew1.rb
"New color for XUV 500 is = Black"