View source for Ruby/C3/Object-Oriented-Programming-Methods/English-timed


{| Border = 1
| | '''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 command'''s, '''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.

|}