Ruby/C2/Ruby-Methods/English-timed

From Script | Spoken-Tutorial
Revision as of 15:09, 10 July 2014 by Pratik kamble (Talk | contribs)

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 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.

Contributors and Content Editors

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