Ruby/C2/Ruby-Methods/English-timed

Time	Narration
00:01	Welcome to the Spoken Tutorial on Ruby Methods.
00:05	In this tutorial, we will learn:
00:07	* What is a method ?
00:09	* Syntax for method and
00:11	we will see some examples.
00:13	Here, we are using: Ubuntu Linux version 12.04 Ruby 1.9.3
00:21	To follow this tutorial, you must have the knowledge of using Terminal and Text editor in Linux.
00:28	Let us now start with an introduction to methods.
00:31	A method is a self-contained program executing a specific task.
00:37	Ruby method is very similar to functions in any other programming language.
00:42	method name should begin with a lowercase letter.
00:45	methods should be defined before calling them.
00:49	Let us see the syntax for method.
00:52	methods are defined using the keyword "def", followed by the method name.
00:57	The arguments specify values that are passed to the method, to be processed.
01:02	ruby code section represents the body of the method that performs the processing.
01:09	The method body is enclosed by this definition on the top and the word "end" on the bottom.
01:16	This is called as method with arguments.
01:19	Another syntax for method is-
01:23	the keyword "def" followed by the method name and an empty argument list,
01:28	ruby code section that represents the body of the method
01:32	and the word "end" that marks the end of method.
01:36	This is called as method without arguments.
01:39	Let's see how to use a method.
01:42	I have already typed a program in the gedit editor.
01:46	Let me open it.
01:48	Please note that our filename is method hyphen without hyphen argument dot rb.
01:55	I have saved this file inside the rubyprogram folder.
01:59	In this program, we will calculate the sum of two numbers using method.
02:03	Let us go through the program.
02:05	Here, we have declared a global variable 'a'
02:08	and we have initialized it by assigning value of 5.
02:13	Global variable names are prefixed with a dollar sign ($).
02:17	Global variables are accessible from anywhere in the Ruby program, regardless of where they are declared.
02:25	Here we have declared a method called add(), without any arguments.
02:31	Here, we ask the user to enter the second number.
02:35	User will enter the value.
02:38	'gets' method, gets the input from the console but in a string format.
02:44	So, we need to convert it into integer, using 'to_i' method.
02:50	The converted value is then stored in the variable 'b'. 'b' is a local variable.
02:56	It is available only to the method inside which it is declared.
03:01	Here, we add the values of global variable 'a' and variable 'b'.
03:07	The result is then stored in the variable sum.
03:10	Then we print the sum.
03:13	This shows a way of inserting a variable within a string.
03:18	Here, the content of sum is returned as a string and is substituted into the outer string.
03:25	end marks the end of the method.
03:28	There are two types of methods.
03:31	User-defined method - that is our add method.
03:35	Pre-defined method - that is print, gets and to_i methods.
03:42	Here, we call our add method.
03:45	The addition operation will be performed and the result will be printed.
03:50	Now, let us click on the Save button.
03:53	This program will be saved in the rubyprogram folder as mentioned earlier.
03:59	Now, let us execute the program.
04:02	Open the terminal by pressing the Ctrl, Alt and T keys simultaneously.
04:07	A terminal window appears on your screen.
04:11	To execute the program, we need to go to the sub-directory rubyprogram.
04:16	So, let's type: cd space Desktop/rubyprogram and press Enter.
04:26	Now, type: ruby space method hyphen without hyphen argument dot rb and press Enter.
04:40	"Enter the second number:" is displayed.
04:44	I will enter the value as 4. Type 4 and press Enter.
04:48	We get the output as - "Sum of two numbers 5 and 4 is 9".
04:53	Now, let us see an example of method with arguments.
04:58	I have already typed this program in the gedit editor, let me open it.
05:03	Please note that our filename is method hyphen with hyphen argument dot rb.
05:10	I have saved this file also inside the rubyprogram folder.
05:15	Let us go through the program.
05:18	Here, we have declared a method called add(). 'a', 'b' are the arguments of the method 'add()'.
05:26	Here, the values of 'a' and 'b' are added
05:29	and the sum is returned to the method called.
05:31	end marks the end of method.
05:35	Here, we are asking the user for input.
05:38	User will enter the values of 'a' and 'b'.
05:41	The values will be stored in variables 'a' and 'b' respectively.
05:46	Here, we call the add method.
05:49	Then we pass the arguments as 'a' and 'b.'
05:52	The value returned by the method 'add()', after performing the addition operation, will be stored in 'c'.
05:59	Here, we print the sum which is stored in 'c'.
06:03	Let's execute this code. Go to the terminal.
06:07	Let us first clear the terminal. Type clear and press Enter.
06:14	We are already in the sub-directory rubyprogram.
06:17	Now, press the up-arrow key twice to get the previous command.
06:22	Replace method hyphen without hyphen arguments dot rb with method hyphen with hyphen arguments dot rb
06:32	and press Enter.
06:35	"Enter the values of a and b" is displayed.
06:38	I will enter 8 and 9.
06:41	Type 8 and press Enter.
06:43	Type 9 and press Enter.
06:46	We get the output as
06:47	"Sum of two numbers 8 and 9 is 17".
06:52	Now, I will show you one important feature of Ruby method.
06:56	Let's go back to the program in the text editor.
06:59	Delete the keyword return.
07:02	Now, click on Save button.
07:05	Let's execute the code. Go to the terminal.
07:09	Press the up-arrow key to get the previous command and press Enter.
07:14	"Enter the values of a and b" is displayed.
07:18	I will enter 10 and 15.
07:21	Type 10, press Enter. Type 15 and press Enter.
07:27	We get the output as
07:29	"Sum of two numbers 10 and 15 is 25".
07:33	We can see that the program is executed without any error, even after deleting the keyword return.
07:40	This is because Ruby automatically returns the value calculated in the method.
07:46	The keyword return in the method is optional in Ruby.
07:50	This brings us to the end of this Spoken Tutorial.
07:53	Let us switch back to our slide.
07:55	Let us summarize.
07:57	In this tutorial, we have learnt:
07:59	* About methods
08:01	* Syntax for method without arguments
08:04	* And method with arguments
08:06	* Returning value from a method.
08:08	As an assignment,
08:10	write a program to calculate area of a square
08:13	by using method and
08:14	by getting the input from the user.
08:17	Watch the video available at the following link.
08:20	It summarizes the Spoken Tutorial project.
08:23	If you do not have good bandwidth, you can download and watch it.
08:28	The Spoken Tutorial project team:
08:30	* Conducts workshops using spoken tutorials.
08:33	* Gives certificates to those who pass an online test.
08:36	For more details, please write to: contact@spoken-tutorial.org
08:44	Spoken Tutorial project is a part of the Talk to a Teacher project.
08:49	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 the below link.
09:00	This is Afrin Pinjari from IIT Bombay, signing off.
09:04	Thank you for watching.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Priyacst, Sandhya.np14, Sneha