Ruby/C3/Object-Oriented-Programming-Methods/English

Title of script: Object Oriented concept in Ruby

Author: Anjana Nair

Keywords: class

Visual Cue	Narration
Slide 1	Welcome to this spoken tutorial on Object Oriented Programming – Methods in Ruby.
Slide 2	In this tutorial we will learn to use: instance methods class methods accessor methods
Slide 3	Here we are using Ubuntu version 12.04 Ruby1.9.3
Slide 4 Pre-requisites	To follow this tutorial, you must have a working Internet connection. You must also have knowledge of Linux commands, Terminal and Text-editor. If not, for relevant tutorials, please visit our website.
	Before we begin, recall that we had created “ttt” directory earlier. Let's go to that directory.
Switch to the terminal which has all the commands for creating the directories and the prompt should be in oop-methods directory	Then to ruby-tutorial. Create a directory named oop-methods and cd into it.
Slide 5 What are instance methods?	What are Instance methods? Instance methods are those methods that are available to all instances of the class. Earlier we had studied how to create objects or instances of a class.
Switch to gedit where you have already opened the file “instance_methods.rb” with the class defnition code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. Name it instance_methods.rb
	I have a working example of the implementing instance methods. You can pause the tutorial, and type the code as we go through it.
Highlight the “initialize” method block	I have defined a class named Product in this example. I have called an initialize method to initialize the instance variables "name" and "price".
Highlight the methods “name” and “price”	I have also defined instance methods named "name" and "price". Each of them return instance variables "name" and "price" respectively.
	Instance methods are defined just like normal methods. Earlier we had studied how to create methods in Ruby. Shortly, we will see how these methods will be available to all instances.
	Now let us implement the logic we have.
Highlight the poduct object creation code.	Here, I have initialized a Product object and named it as product_object_1. I have initialized it with a name value and a price value.
Highlight the initialize block.	The initializer block passes the values to the instance variables @name and @price.
Highlight : puts product_object_1.name puts product_object_1.price	Now this product instance or object can use the instance methods name and price. On invoking these methods, we get the values stored in the instance variables.
On the terminal type- ruby instance_methods.rb >> press Enter	Now let us execute this code. Switch to the terminal and type: ruby instance_methods.rb and press Enter to see the output.
Point to the output.	You will see that it will print the values you initialized the object with. Namely, laptop and 35,000.
Highlight the initialization of product_object_2	Next, initialize another instance or object. Let us name this object product_object_2. This time, let us give a different set of values for name and price.
Highlight the puts statements	Now let us call the instance methods "name" and "price"” for this object.
Switch to the terminal >> Press up-arrow >> Enter.	Next let us switch back to the terminal and execute the code like before.
Output on the terminal.	You will notice that it executes successfully and it prints out the new values. This proves that instance methods are available to all objects of the class Product.
	You should now be able to write your own instance methods.
	Next, let us look at what class methods are.
Slide 6 What are class methods	Class methods are methods available only to the class. These methods are not available to instances of the class. There are different ways you can define class methods.
	Let us look at an example.
Switch to gedit where you have already opened the file “class_methods.rb” with the class defnition code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. Name it class_methods.rb
	I have a working example of class methods. You can pause the tutorial, and type the code as we go through it.
Highlight Product.	I have defined a Product class like before.
Highlight the initialize code block.	I have also called an initializer like before. However, this time I have added an extra argument called description. I am also using class variables to hold the values unlike instance variables, earlier.
Highlight the first class declaration code.	This class will demonstrate to you the 3 different ways one can define class methods. Checkout the class method declaration for name. Here it is defined using the class name "Product".
Highlight the second class declaration code.	Then, checkout the second class methods declaration. Here I have used the "self" keyword.
Highlight the second class declaration code.	Next, checkout the third way you can define class methods.
	Now let us implement these class methods.
Highlight the object creation logic.	Let us first initialize an object of Product, like before. This time we are also giving a value for the description.
Highlight the lines corresponding the class method invocation.	Now let us invoke the class methods as shown here.
	Now let us execute the code and inspect the output.
Switch to the terminal >> type ruby class_methods.rb >> Enter.	Switch to the terminal and execute the code like before.
Output on the terminal.	You will notice that it will print the values for name, price and description.
	Now you should be able to write your own class methods. <<PAUSE>>
	Next we shall see what accessor methods are.
Slide 5 What are accessor methods	Ruby uses accessor methods to access data defined within classes. Accessor methods comprise of setter methods and getter methods. Setter methods set the values. Getter methods get those values. Ruby uses the word attr_accessor to declare these methods.
	Let us look at an example of accessor methods.
Switch to gedit where you have already opened the file “accessor_methods.rb” with the class defnition code typed inside.	Create a new file in gedit as shown in the basic level Ruby tutorials. Name it accessor_methods.rb
	I have a working example of the implementing accessor methods. You can pause the tutorial, and type the code as we go through it.
Highlight “attr_accessor” line	I have defined a class named Product, in this example. I have declared attr_accessor for name and price. That is all that is required to use these types of methods.
Highlight object creation logic.	Now let us put it to action. I have initialized a Product object.
Highlight the setter logic.	Then, I have set the name and price of the product object. This is possible because the attr_declaration, by default, creates methods for setting values.
Highlight the getter logic.	I have then attempted to print the values using the getter methods for name and price. These getter methods were also generated by the declaration of attr_accessor.
	Now let us execute the code like before.
	You will notice that it prints the values that were set.
	By now, you should be able to write your own accessor methods.
Slide Accessor Methods	One thing to note is that accessor methods are, by default, instance methods. Thus they can be accessed by different instances of the class Product.
Slide Summary	In this tutorial we have learnt about: instance methods class methods and accessor methods
Slide Assignment	As an assignment: Define a class named Temperature Write an instance method using Ruby's accessor method syntax. This method should calculate the Celsius for the given Fahrenheit.
Slide About the Spoken Tutorial Project	Watch the video available at the following link. It summarizes the Spoken Tutorial project. If you do not have good bandwidth, you can download and watch it.
Slide	The Spoken Tutorial Project Team : Conducts workshops using spoken tutorials Gives certificates to those who pass an online test For more details, please write to contact at spoken hyphen tutorial dot org
Slide Acknowledgments	Spoken Tutorial Project is a part of the Talk to a Teacher project. It is supported by the National Mission on Education through ICT, MHRD, Government of India. More information on this Mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro.
Previous Slide	This is Anjana Nair signing off. Thank you

Contributors and Content Editors

Anjana, Nancyvarkey