Difference between revisions of "Ruby/C2/Variables-in-Ruby/English-timed"

|   Welcome to the Spoken Tutorial on Variables in '''Ruby'''  

| In this tutorial we will learn

| What is a variable?

 

|  Dynamic typing in '''Ruby'''

| Declaring a variable

| Converting variable types  

| What is variable's scope?

| Types of variables

|  Here we are using '''Ubuntu Linux version 12.04'''   '''Ruby''' 1.9.3

|  To follow this tutorial you must have the knowledge of using''' Terminal''' in '''Linux.'''

 

| You must also be familiar with '''irb'''

 

| If not, for relevant tutorials, please visit our website

 

|  Now I will explain what a variable is.

|  Please note that '''Ruby '''variables are''' case sensitive.'''

|  Now let us see what is dynamic typing

|  It means that you don't need to declare '''datatype''' while creating a variable.

|  '''Ruby interpreter '''determines the data type at the time of assignment.

 

 

|  Now let us see how to declare a variable in '''Ruby.'''

|  Open the terminal by pressing '''Ctrl, Alt''' and''' T '''keys simultaneously.

 

| A terminal window appears on your screen.

|  Now, type '''irb'''

| Press '''Enter '''to launch '''Interactive Ruby'''

|  Now type '''var1''' equal to 10  and Press '''Enter'''

|  Here we have declared a variable '''var1''' and assigned a value '''10 ''' to it.

|  So, type '''var1'''  dot  '''kind'''_(underscore)'''of '''(?)question mark '''Integer''' and press '''Enter'''

|  We will get the output as '''true.'''

|  In''' Ruby''' you can dynamically change the variable type.

|   Type '''var1''' equal to within double quote '''hello'''and   press Enter

| Let's verify the variable type assigned  

| Type  '''var1''' dot '''class '''

 

| Class method tells us what class of variable it is. Now Press''' Enter'''

|  We get the output as '''string'''

|  '''Ruby '''has automatically changed the variable type from '''integer''' to '''string'''

|  We will now learn how to convert a variable value to different type  

| Lets switch back to slides

 

| '''Ruby''' variable classes have methods to convert their value to a different type

|  '''to_i '''method is used to convert a variable to '''integer'''

|  '''to_f '''method is used to convert a variable to '''floating point value'''

|  '''to_s''' method is used to convert a variable to''' string'''  

 

|  '''to _s''' method takes number base as an argument.

|  Now let us try out these methods.

| Go to the''' terminal'''  Lets clear the terminal first

| Press Ctrl L to clear the '''irb '''console  

 

| Now  Type '''y '''equal to '''20'''  and Press '''Enter'''

|  Here we have declared a variable called''' y''' and assigned a value '''20''' to it.

| We will now convert '''y''' to a floating point value using '''to '''underscore''' f''' method

|  Type '''y '''dot '''to '''underscore '''f''' and  Press '''Enter'''

| We will get the value as float'''.'''

|  Now Type '''y dot '''to '''underscore s''' and Press '''Enter'''

|  We will get output '''20 '''within double quotes

| To convert variable '''y''' in binary form give number base as '''2''' in '''to_s''' method

| Press up arrow key to get the previous command  

|  Type opening bracket 2 closing bracket and  press '''Enter'''

| We get the output in the binary form

|   Similarly you can convert variable '''y''' to '''octal''' or '''hexadecimal''' form  

| By changing the number base to 8 or 16.

|  Let us switch back to our slide

| '''Scope''' defines where in a program a variable is accessible.

 

| '''Ruby''' has four types of variable scope:

| Local

 

| 06:01

|Global  

| Instance and

| Class

|  Each variable type is declared by using a special character at the beginning of the variable name  

 

|   06:14

| '''$ '''represents ''' global''' variable  

| Lower case letters and underscore represents a '''local''' variable

| '''@''' represents an '''instance''' variable  

| Two''' @@''' symbols represents a '''class''' variable  

| Upper case letters represents a '''constant'''

 

| We will learn in detail about this in another tutorial.

|  This brings us to the end of this Spoken Tutorial. Let us summarises

| In this tutorial we have learnt

| To declare a variable   eg var1=10

| Changing variable type using to_f, to_s methods

| Different Variable '''scope'''

 

 

| As an assignment

| Declare a variable and convert it to '''octal''' and '''hexadecimal''' form

 

 

 

| It summarises the Spoken Tutorial project.

|  The Spoken Tutorial Project Team :

 

| Conducts workshops using spoken tutorials  

| Gives certificates to those who pass an online test  

| For more details, please write to contact at spoken hyphen tutorial dot org

| Spoken Tutorial Project is a part of the Talk to a Teacher project.

| More information on this Mission is available at the below link

| This is Afrin Pinjari from IIT Bombay, signing off.

 

Thank you for watching.