cseiter/Phase3SetterAndGetter

Setter and Getter Methods

Learning Goals

• Learn more about setter and getter methods
• Build and use setter and getter methods

Introduction

So far, we've learned how to build classes and give them instance methods. We also learned how to create instance variables and use setter and getter methods to set and retrieve their values, respectively. In this lesson, we'll learn more about these methods and why they're important.

Setters and Getters

Setter and getter methods are integral to object-oriented programming in Ruby. They are what enable us to assign attributes to our objects (e.g., name or breed) and retrieve the value of those attributes.

To review, if we have a Person class, our setter and getter for the name attribute will look like this:

class Person

  def name=(name)
    @name = name
  end

  def name
    @name
  end

end

Note that the setter method is defined with an = (equals sign) appended to the name of the method. The = is then followed by the parameter, name, in parentheses. The = in the method definition line is part of the method's name; it is simply a character that identifies this method as a setter method. The actual assignment — the use of the operator = to set a value — happens inside the method.

What this means is that, if we were to create a Person instance and then use the usual Ruby syntax to call the setter method and pass it an argument, our code would look like this:

kanye = Person.new
kanye.name=("Kanye")

Note that this is exactly the same as calling any method that takes an argument on any object:

any_object.any_method(arg)

The only difference is the = that is part of our method's name, identifying it as a setter method.

We don't have to use this syntax to call our setter method, however. Instead, Ruby provides us a bit of syntactic sugar for setter methods that enables us to do this:

kanye = Person.new
kanye.name = "Kanye"

This syntax is easier to read and more intuitive and is therefore preferred.

Finally, to ask our kanye object to return the value of its name attribute, we would do this:

kanye.name #=> "Kanye"

Here we are calling the getter method, name, that belongs to every instance of our Person class.

Lab

Fork and clone the lab and run learn test. To get the tests passing, you will need to complete the following tasks:

Dog and lib/dog.rb

1. Add a getter and setter method for the instance variable @name.
2. Add a getter and setter method for the instance variable @breed.

Person and lib/person.rb

1. Add a getter and setter method for the instance variable @name.
2. Add a getter and setter method for the instance variable @job.

Phase3SetterAndGetter