From Script | Spoken-Tutorial
Jump to: navigation, search

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 '"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 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:
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