Difference between revisions of "Ruby/C2/Variables-in-Ruby/English-timed"
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Revision as of 06:51, 18 November 2015
| 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? |
| 00:10 | * 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:
|
| 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 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". |
| 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 slides. |
| 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 will get the value as float. |
| 04:57 | Now, type: y dot to underscore s and press Enter. |
| 05:06 | We will get output 20, within double quotes. |
| 05:10 | To convert variable 'y' in binary form, give number base as 2 in to_s method. |
| 05:18 | Press 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 scope: |
| 06:00 | * Local |
| 06:01 | * 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 represents 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 variable type using to_f, 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 at 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. |
