Ruby/C3/Object-Oriented-Programming-Methods/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this spoken tutorial on Object Oriented Programming – Methods in Ruby. |
| 00:07 | In this tutorial, we will learn to use: |
| 00:09 | instance methods |
| 00:11 | class methods, accessor methods. |
| 00:15 | Here, we are using: Ubuntu version 12.04 |
| 00:19 | Ruby 1.9.3 |
| 00:22 | To follow this tutorial, you must have a working Internet connection. |
| 00:27 | You must also have knowledge of Linux commands, Terminal and Text-editor. |
| 00:31 | If not, for relevant tutorials, please visit our website. |
| 00:36 | Before we begin, recall that we had created “ttt” directory earlier. |
| 00:41 | Let's go to that directory. |
| 00:44 | Then to ruby-tutorial. |
| 00:47 | Create a directory named oop-methods and cd into it. |
| 00:54 | What are Instance methods? |
| 00:56 | Instance methods are those methods that are available to all instances of the class. |
| 01:03 | Earlier we had studied how to create objects or instances of a class. |
| 01:09 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
| 01:14 | Name it instance_methods.rb. |
| 01:19 | I have a working example of implementing instance methods. |
| 01:24 | You can pause the tutorial and type the code as we go through it. |
| 01:29 | I have defined a class named Product in this example. |
| 01:33 | I have called an initialize method to initialize the instance variables, "name" and "price". |
| 01:41 | I have also defined instance methods named "name" and "price". |
| 01:47 | Each of them return instance variables "name" and "price" respectively. |
| 01:54 | Instance methods are defined just like normal methods. |
| 01:58 | Earlier we had studied how to create methods in Ruby. |
| 02:02 | Shortly, we will see how these methods will be available to all instances. |
| 02:07 | Now, let us implement the logic we have. |
| 02:11 | Here, I have initialized a Product object and named it as "product_object_1". |
| 02:18 | I have initialized it with a name value and a price value. |
| 02:24 | The initializer block passes the values to the instance variables "@name" and "@price". |
| 02:31 | Now, this product instance or object can use the instance methods name and price. |
| 02:37 | On invoking these methods, we get the values stored in the instance variables. |
| 02:43 | Now, let us execute this code. |
| 02:46 | Switch to the terminal and type: ruby instance_methods.rb and press Enter to see the output. |
| 02:56 | You will see that it will print the values you initialized the object with. |
| 03:02 | Namely, "laptop" and "35,000". |
| 03:07 | Next, initialize another instance or object. |
| 03:12 | Let us name this object product_object_2. |
| 03:18 | This time, let us give a different set of values for name and price. |
| 03:23 | Now, let us call the instance methods- "name" and "price" for this object. |
| 03:35 | Next, let us switch back to the terminal and execute the code like before. |
| 03:41 | You will notice that it executes successfully and it prints out the new values. |
| 03:48 | This proves that instance methods are available to all objects of the class Product. |
| 03:55 | You should now be able to write your own instance methods. |
| 03:59 | Next, let us look at what class methods are. |
| 04:04 | Class methods are methods available only to the class. |
| 04:09 | These methods are not available to instances of the class. |
| 04:14 | There are different ways you can define class methods. |
| 04:16 | Let us look at an example. |
| 04:18 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
| 04:24 | Name it class_methods.rb. |
| 04:28 | I have a working example of class methods. |
| 04:32 | You can pause the tutorial and type the code as we go through it. |
| 04:36 | I have defined a Product class like before. |
| 04:40 | I have also called an initializer, like before. |
| 04:44 | However, this time I have added an extra argument called description. |
| 04:48 | I am also using class variables to hold the values, unlike instance variables earlier. |
| 04:55 | This class will demonstrate to you the 3 different ways one can define class methods. |
| 05:01 | Checkout the class method declaration for name. |
| 05:06 | Here, it is defined using the class name "Product". |
| 05:10 | Then, checkout the second class methods declaration. |
| 05:14 | Here I have used the "self" keyword. |
| 05:18 | Next, checkout the third way you can define class methods. |
| 05:23 | Now let us implement these class methods. |
| 05:27 | Let us first initialize an object of Product, like before. |
| 05:32 | This time we are also giving a value for the description. |
| 05:37 | Now, let us invoke the class methods as shown here. |
| 05:42 | Now, let us execute the code and inspect the output. |
| 05:47 | Switch to the terminal and execute the code like before. |
| 05:54 | You will notice that it will print the values for name, price and description. |
| 05:59 | Now, you should be able to write your own class methods. |
| 06:03 | Next we shall see what accessor methods are. |
| 06:07 | Ruby uses accessor methods to access data, defined within classes. |
| 06:13 | Accessor methods comprise of setter methods and getter methods. |
| 06:18 | Setter methods set the values. |
| 06:22 | Getter methods get those values. |
| 06:24 | Ruby uses the word attr_accessor to declare these methods. |
| 06:31 | Let us look at an example of accessor methods. |
| 06:35 | Create a new file in gedit as shown in the basic level Ruby tutorials. |
| 06:39 | Name it accessor_methods.rb |
| 06:43 | I have a working example of implementing accessor methods. |
| 06:47 | You can pause the tutorial and type the code as we go through it. |
| 06:52 | I have defined a class named Product, in this example. |
| 06:56 | I have declared attr_accessor for 'name' and 'price'. |
| 07:01 | That is all that is required to use these types of methods. |
| 07:05 | Now let us put it to action. |
| 07:07 | I have initialized a Product object. |
| 07:10 | Then, I have set the name and price of the product object. |
| 07:14 | This is possible because the attr_declaration, by default, creates methods for setting values. |
| 07:22 | I have then attempted to print the values using the getter methods for 'name' and 'price'. |
| 07:28 | These getter methods were also generated by the declaration of attr_accessor. |
| 07:35 | Now let us execute the code like before. |
| 07:40 | You will notice that it prints the values that were set. |
| 07:44 | By now, you should be able to write your own accessor methods. |
| 07:50 | One thing to note is that accessor methods are, by default, instance methods. |
| 07:55 | Thus they can be accessed by different instances of the class Product. |
| 08:00 | In this tutorial, we have learnt about: instance methods, class methods and accessor methods. |
| 08:06 | As an assignment: define a class named Temperature. |
| 08:10 | Write an instance method using Ruby's accessor method syntax. |
| 08:15 | This method should calculate the Celsius for the given Fahrenheit. |
| 08:20 | Watch the video available at the following link. |
| 08:23 | It summarizes the Spoken Tutorial project. |
| 08:26 | If you do not have good bandwidth, you can download and watch it. |
| 08:30 | The Spoken Tutorial project team: Conducts workshops using spoken tutorials. |
| 08:34 | Gives certificates to those who pass an online test. |
| 08:38 | For more details, please write to:contact at spoken hyphen tutorial dot org. |
| 08:44 | Spoken Tutorial project is a part of the Talk to a Teacher project. |
| 08:48 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 08:55 | More information on this mission is available at: spoken hyphen tutorial dot org slash NMEICT hyphen Intro. |
| 09:03 | This is Anjana Nair, signing off. Thank you. |
