Ruby/C2/Ruby-Methods/English-timed
From Script | Spoken-Tutorial
| 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: 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. |
