Difference between revisions of "Ruby/C2/Ruby-Methods/English-timed"
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Revision as of 15:36, 13 November 2014
| 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 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 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 the 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 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 method. |
| 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 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 subdirectory 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 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 call. |
| 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 variable 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 store in c. |
| 06:03 | Lets 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 subdirectory 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 method is optional in Ruby. |
| 07:50 | This brings us to the end of this Spoken Tutorial. |
| 07:53 | Let us switch back to slides |
| 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 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 user |
| 08:17 | Watch the video available at the following link. |
| 08:20 | It summarises 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. |
