Ruby/C2/Variables-in-Ruby/English-timed
From Script | Spoken-Tutorial
Revision as of 14:48, 2 June 2014 by PoojaMoolya (Talk | contribs)
| 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 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 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 data type 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 will 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 quote helloand 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 | Lets 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 Lets 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 represents a class variable |
| 06.33 | Upper case letters represents 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 summarises |
| 06.48 | In this tutorial we have learnt |
| 06.51 | To declare a variable eg var1=10 |
| 06.56 | Changing variable type using to_f, to_s methods |
| 07.04 | Different Variable scope
|
| 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 summarises 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. |
