From Script | Spoken-Tutorial
Jump to: navigation, search
Time Narration
00:02 Welcome to the Spoken Tutorial on Variables in Ruby.
00:06 In this tutorial, we will learn:
00:09 What is a variable? Dynamic typing in Ruby
00:13 Declaring a variable
00:15 Converting variable types
00:18 What is variable's scope?
00:20 Types of variables.
00:23 Here, we are using: Ubuntu Linux version 12.04, Ruby 1.9.3
00:32 To follow this tutorial, you must have the knowledge of using Terminal in Linux.
00:38 You must also be familiar with "irb".
00:41 If not, for relevant tutorials, please visit our website.
00:47 Now, I will explain you what a variable is.
00:50 Variable is used to store a value.
00:54 Variable is a reference that can be assigned.
00:58 Please note that Ruby variables are case sensitive.
01:04 Variable names should be meaningful.
01:07 Variable name may only contain lowercase letters, numbers, underscores. Ex : first_name
01:20 Now, let us see what is dynamic typing.
01:23 Ruby is a dynamic typed language.
01:27 It means that you don't need to declare datatype while creating a variable.
01:34 Ruby interpreter determines the datatype at the time of assignment.
01:39 Now, let us see how to declare a variable in Ruby.
01:45 Open the terminal by pressing Ctrl, Alt and T keys simultaneously.
01:51 A terminal window appears on your screen.
01:55 Now, type "irb" and
01:57 press Enter to launch Interactive Ruby.
02:02 Now, type: var1 equal to 10 and press Enter.
02:09 Here, we have declared a variable var1 and assigned a value 10 to it.
02:15 Let's check whether the datatype allotted by the interpreter is integer or not.
02:21 So, type: var1 dot kind_(underscore)of (?)question mark Integer and press Enter.
02:37 We get the output as "true".
02:39 In Ruby, you can dynamically change the variable type.
02:44 To do so, just assign a new value to it.
02:47 Let's do this by assigning a string value to variable var1.
02:53 Type: var1 equal to within double quotes hello and press Enter.
03:02 Let's verify the variable type assigned.
03:06 Type: var1 dot class .
03:12 Class method tells us what class of variable it is. Now press Enter.
03:20 We get the output as "String".
03:23 Ruby has automatically changed the variable type from integer to string.
03:29 We will now learn how to convert a variable value to different type.
03:35 Let's switch back to slide.
03:38 Ruby variable classes have methods to convert their value to a different type.
03:45 'to_i' method is used to convert a variable to integer.
03:51 'to_f' method is used to convert a variable to floating point value.
03:57 'to_s' method is used to convert a variable to string.
04:03 'to _s' method takes number base as an argument.
04:08 The conversion depends on this number base.
04:12 Now, let us try out these methods.
04:15 Go to the terminal. Let's clear the terminal first.
04:21 Press Ctrl, L to clear the irb console.
04:25 Now, type: y equal to 20 and press Enter.
04:32 Here, we have declared a variable called 'y' and assigned a value 20 to it.
04:39 We will now convert 'y' to a floating point value using to underscore f method.
04:47 Type: y dot to underscore f and press Enter.
04:55 We get the value as float.
04:57 Now, type: y dot to underscore s and press Enter.
05:06 We get the output as 20, within double quotes.
05:10 To convert variable 'y' in binary form, give number base as 2 in the to_s method.
05:18 Press the up-arrow key to get the previous command.
05:22 Type: opening bracket 2 closing bracket and press Enter.
05:29 We get the output in the binary form.
05:33 Similarly, you can convert variable 'y' to octal or hexadecimal form
05:39 by changing the number base to 8 or 16.
05:44 Let us switch back to our slide.
05:47 We will now learn what is a variable scope.
05:51 Scope defines- where in a program, a variable is accessible.
05:56 Ruby has four types of variable scopes:
06:00 Local, Global
06:02 Instance and
06:04 Class.
06:06 Each variable type is declared by using a special character at the beginning of the variable name.
06:14 '$' represents global variable.
06:18 Lower case letters and underscore represent a local variable.
06:25 '@' represents an instance variable.
06:29 Two '@@' symbols represent a class variable.
06:33 Upper case letters represent a constant.
06:37 We will learn in detail, about this, in another tutorial.
06:42 This brings us to the end of this Spoken Tutorial. Let us summarize.
06:48 In this tutorial, we have learnt:
06:51 To declare a variable, e.g. var1=10
06:56 Changing a variable type using 'to_f' and 'to_s' methods
07:04 Different variable scopes.
07:06 As an assignment,
07:08 declare a variable and convert it to octal and hexadecimal form.
07:14 Watch the video available at the following link.
07:17 It summarizes the Spoken Tutorial project.
07:20 If you do not have good bandwidth, you can download and watch it.
07:24 The Spoken Tutorial project team :
07:27 Conducts workshops using spoken tutorials.
07:30 Gives certificates to those who pass an online test.
07:34 For more details, please write to: contact @ spoken hyphen tutorial dot org.
07:41 Spoken Tutorial project is a part of the Talk to a Teacher project.
07:45 It is supported by the National Mission on Education through ICT, MHRD, Government of India.
07:51 More information on this mission is available at the below link.
07:57 This is Afrin Pinjari from IIT Bombay, signing off. Thank you for watching.

Contributors and Content Editors

PoojaMoolya, Pratik kamble, Sandhya.np14, Sneha