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 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. |
| 00.46 | Methods should be defined before calling them. |
| 00.50 | 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.
|
| 01.03 | The ruby code section represents the body of the method that performs the processing.
|
| 01.10 | 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. |
| 01.20 | Another syntax for method is
|
| 01.23 | The keyword def followed by the method name and an empty argument list
|
| 01.29 | The 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. |
| 01.40 | Let's see how to use a method. |
| 01.43 | I have already typed a program in the gedit editor. |
| 01.47 | Let me open it. |
| 01.48 | Please note that our filename is method-without-argument.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. |
| 02.04 | Let us go through the program. |
| 02.06 | Here we have declared a global variable a. |
| 02.09 | 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. |
| 02.36 | 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. |
| 02.57 | It is available only to the method inside which it is declared. |
| 03.02 | Here we add the values of global variable a and variable b. |
| 03.07 | The result is then stored in variable sum. |
| 03.11 | 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. |
| 03.26 | end marks end of the method. |
| 03.29 | There are two types of methods. |
| 03.32 | 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 ouradd 'method. |
| 03.46 | The addition operation will be performed and the result will be printed. |
| 03.50 | Now let us click on the Save. |
| 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. |
| 04.08 | A terminal window appears on your screen. |
| 04.11 | To execute the program, we need to go to the subdirectory rubyprogram. |
| 04.17 | So let's type cd space Desktop/rubyprogram and press Enter. |
| 04.26 | Now Type ruby space method-without-argument.rb and press Enter |
| 04.41 | 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. |
| 05.04 | Please note that our filename is method-with-argument.rb |
| 05.10 | I have saved this file also inside the rubyprogram folder. |
| 05.16 | 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. |
| 05.32 | end marks the end of method. |
| 05.36 | Here we are asking the user for input. |
| 05.40 | User will enter the values of a and b. |
| 05.42 | The values will be stored in variable a and variable b, respectively. |
| 05.47 | Here we call the add method |
| 05.49 | Then we pass the arguments as a and b. |
| 05.53 | The value returned by the method add , after performing the addition operation will be stored in c. |
| 06.00 | Here we print the sum which is store in c. |
| 06.04 | Lets execute this code. Go to the terminal. |
| 06.08 | 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-without-arguments.rb with method-with-arguments.rb |
| 06.33 | And Press Enter |
| 06.35 | Enter the values of a and b is displayed. |
| 06.39 | 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. |
| 06.57 | Let's go back to the program in the text editor. |
| 07.00 | Delete the keyword return. |
| 07.03 | 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. |
| 07.15 | Enter the values of a and b 'is displayed. |
| 07 .18 | I will enter 10 and 15. |
| 07.22 | Type 10 and press Enter Type 15 and press Enter |
| 07.28 | We get the output as |
| 07.29 | Sum of two numbers10 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 |
| 07.56 | Let's summarize |
| 07.58 | In this tutorial we have learnt |
| 08.00 | About Methods |
| 08.01 | Syntax for Method without arguments |
| 08.04 | And Method with arguments |
| 08.06 | Returning value from method |
| 08.09 | As an assignment |
| 08.10 | Write a program,to calculate area of a square
|
| 08.13 | by using method and |
| 08.15 | by getting the input from user |
| 08.17 | Watch the video available at the following link. |
| 08.20 | It summarises the Spoken Tutorial project. |
| 08.24 | If you do not have good bandwidth, you can download and watch it. |
| 08.29 | The Spoken Tutorial Project Team :
|
| 08.31 | Conducts workshops using spoken tutorials |
| 08.33 | Gives certificates to those who pass an online test |
| 08.36 | For more details, please write to |
| 08.45 | 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: spoken-tutorial.org/NMEICT-Intro. |
| 09.00 | This is Afrin Pinjari from IIT Bombay, signing off. |
| 09.05 | Thank you for watching. |
