Ruby/C3/Object-Oriented-Concept-in-Ruby/English-timed

Time'	Narration
00.01	Welcome to this spoken tutorial on Object Oriented Concept in Ruby.
00.06	In this tutorial we will learn to use-
00.08	classes
00.09	creating objects
00.10	different ways of defining methods in Ruby
00.13	Here we are using
00.14	Ubuntu version 12.04
00.16	Ruby 1.9.3
00.19	To follow this tutorial, you must have knowledge of Linux commands, Terminal and Text-editor.
00.24	If not, for relevant tutorials, please visit our website.
00.28	Before we begin, recall that we had created a “ttt” directory earlier.
00.33	Let's go to that directory.
00.35	To ruby hyphen tutorial and classes directory.
00.41	Ruby is an object oriented language.
00.44	Everything in Ruby is an object; from a value to a string or number.
00.49	A class' is a collection of related data and functions.
00.53	It can serve to keep information organized.
00.56	An object is an instantiation of a class.
01.00	A class definition begins with the keyword class.
01.05	It is followed by the name of the class.
01.08	It is delimited with an “end”.
01.11	Let us look at an example of a class.
01.14	class Product
01.16	ruby code
01.17	end
01.20	The name of the class must begin with a capital letter.
01.24	Names that contain more than one word should be camelcased.
01.28	For example,
01.30	UserInformation
01.32	ProductInformation
01.34	The subsequent file names will have underscore separating the words:
01.37	user underscore information
01.40	product underscore information
01.45	Create a new file in gedit as shown in the basic level Ruby tutorials.
01.48	Name it class_definition.rb
01.52	I have a working example of the implementation of classes.
01.57	You can pause the tutorial, and type the code as we go through it.
02.02	I have defined a class named Order in this example.
02.05	Now let us make the class useful by adding some variables.
02.11	Then I have defined an instance variable “myinstance”.
02.15	And I have assigned a value to it.
02.18	I have also defined a class variable “myclassvar”
02.21	And I have assigned a value to it.
02.24	Now let us add some code that will make use of this class.
02.30	Type puts Order dot instance underscore variables.
02.36	Before this line, add puts some characters slash n for a new line.
02.43	Let us copy and paste that and add it just below the line we added and save it.
02.51	Now let us execute this code
02.53	Switch to the terminal and type
02.56	ruby space class underscore definition dot rb
03.02	and see the output.
03.05	You will see the instance variable you defined.
03.09	Now let us type puts Order dot class underscore variables.
03.15	Let us copy and paste the demarcation, just below the line and save it.
03.21	Now let us switch to the terminal and execute the file like before.
03.26	You will notice the class variable you defined, also show up.
03.32	To now be able to write your own class.
03.35	Next, let us look at what an object is.
03.40	An object is an instance of a class.
03.43	Which means an object is created from a class.
03.46	An object will have the properties and methods defined in the class.
03.52	How do you declare an object
03.54	We declare an object of a class using the new keyword.
03.58	Here we are declaring an object of the Product class.
04.02	Here an object gets created.
04.05	product = Product.new
04.09	This process is called initialization of an object.
04.12	This object is of type: Product.
04.16	Now let is look at what an “initialize” method is.
04.20	An initialize method is called at the time of object creation.
04.26	On calling new on an object, we invoke the initialize method.
04.31	An initialize method may take a list of parameters.
04.37	Like other Ruby methods, it is preceded by the “def” keyword.
04.43	Let us look at an example.
04.46	Create a new file in gedit as shown in the basic level Ruby tutorials.
04.50	And name it object undescore initialize dot rb
04.55	I have a working example of the object initialization code.
05.00	You can pause the tutorial, and type the code as we go through it.
05.04	Here I have defined a class called “Order”
05.08	Then I have defined the initialize method, with no argument.
05.13	I have defined a puts method to display the message “I have created an object”.
05.20	Next, I have defined Order dot new.
05.24	This will invoke the initialize method.
05.27	Switch to the terminal and type
05.31	ruby space object underscore initialize dot rb
05.36	and see the output.
05.39	You will see the message “I have created an object” .
05.43	Now let us go back to gedit and add an argument to the method.
05.48	Let us modify the puts .
05.51	It should display the value of the argument passed.
05.55	Next let us type
05.56	Order dot new(“I have created an object”).
06.04	Here we have given an argument to the new method.
06.08	This argument gets passed on to the initialize method.
06.13	Switch to the terminal and type
06.16	ruby space object underscore initialize dot rb
06.20	and see the output.
06.22	You will see the message “I have created an object” printed out.
06.29	Now, you would have understood what object initialization means.
06.33	Recall that in Ruby, methods are the functions that a class performs.
06.39	Each method in a class is defined within the “def” and “end” block.
06.45	A multiword method name is separated with an underscore.
06.48	Some of the characters that can be appended to a method name are:
06.54	? (question-mark)
06.56	= (equal to)
06.58	Each of the characters add some meaning to the method.
07.02	Let us look at some examples.
07.05	Create a new file in gedit as shown in the basic level Ruby tutorials.
07.09	And name it class underscore methods dot rb.
07.14	I have a working example of class methods code.
07.17	You can pause the tutorial, and type the code as we go through it.
07.21	Here I have defined a class named “Animal”.
07.23	Then I have two methods “breathe” and “walk”.
07.28	They are both defined with the “def” and “end” keywords.
07.32	I have then initialized the object Animal.
07.36	I have assigned it to a variable called “animal” with lowercase “a”.
07.40	Then I have invoked the methods “breathe” and “walk” consequtively.
07.48	Now let us execute the program.
07.51	Switch to the terminal and type
07.53	ruby space class underscore methods dot rb
07.58	and see the output.
08.00	You will notice the lines:
08.02	“ I breathe”
08.03	“ I walk”
08.04	printed out.
08.05	This is because you have invoked the two methods “breathe” and “walk”.
08.10	A “puts” statement defined within these methods gives the results you see.
08.16	Next, let us look at how to create methods with a trailing question mark.
08.21	Create a new file in gedit as shown in the basic level Ruby tutorials.
08.25	And name it class underscore methods underscore with underscore trailing underscore characters dot rb
08.35	I have a working example of class methods with question mark code.
08.40	You can pause the tutorial, and type the code as we go through it.
08.45	Here I have taken the same class as before as an example.
08.48	Here the breathe method has a trailing “question mark (?)”.
08.52	Such methods are generally used to return boolean values.
08.55	This is based on the method naming convention of Ruby.
09.00	The method gets invoked by declaring animal dot breathe question-mark
09.06	Switch to the terminal and type
09.09	ruby space class underscore methods underscore with underscore trailing underscore characters dot rb and see the output.
09.22	You will notice the output as : “true”
09.26	Next, let us define another method called “walk”.
09.30	Let us place an equal-to sign “=(value)” beside it.
09.36	Let us invoke this method by calling animal dot walk.
09.41	Then let us execute this method.
09.44	Switch to the terminal and type
09.45	ruby class underscore methods underscore with underscore trailing underscore characters dot rb
09.52	and see the output.
09.56	It will give an “undefined method” error.
09.59	This is because the equal to sign has another meaning.
10.03	It is used to assign a value to a method.
10.08	So, let us invoke the method a little differently this time.
10.13	Type puts animal dot walk equal to “ hops”
10.17	Now let give it another try.
10.20	Switch to the terminal and run the command like before and see the output.
10.27	You will notice that the word “hops” get printed.
10.30	This demonstrates that the equal to sign next to a method means assignment.
10.36	Now you should be able to write your own methods.
10.42	In this tutorial we have learnt-
10.44	How to declare classes
10.46	How to create objects of a class
10.48	Different ways of defining methods in Ruby
10.52	As an assignment:
10.54	Define a class Product
10.56	Define methods that you can use to get values of “myvar” and set values for “myvar”.
11.01	To set values, define the method using “=” sign.
11.05	Instantiate the object of the class and set and get values using the above 2 methods.
11.12	Watch the video available at the following link.
11.14	It summarises the Spoken Tutorial project.
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11.22	The Spoken Tutorial Project Team :
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11.36	Spoken Tutorial Project is a part of the Talk to a Teacher project.
11.39	It is supported by the National Mission on Education through ICT, MHRD, Government of India.
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11.56	This is Anjana Nair signing off. Thank you

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Jyotisolanki, PoojaMoolya, Pratik kamble, Sandhya.np14, Shruti arya