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

Learning Objectives

• What is a variable?
• Dynamic typing in Ruby
• Declaring a variable
• Converting variable types
• What is variable's scope?
• Types of variables

System Requirements

• Ubuntu Linux version 12.04
• Ruby 1.9.3

Pre-requisites

You must also be familiar with irb

If not, for relevant tutorials, please visit our website

Variables

• Variable is used to store a value.
• Variable is a reference that can be assigned.
• Please note that Ruby variables are case sensitive.

Variables

• Variable name may only contain lowercase letters, numbers and underscores.
• Ex : first_name

Dynamic Typing

• Ruby is a dynamic typed language.
• 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.

Switch to the terminal

A terminal window appears on your screen.

irb<<Press Enter

irb

Press Enter to launch Interactive Ruby

var1=10 <<press Enter

var1 equal to 10

Press Enter

Highlight 10

integer or not .

var1.kind_of?Integer << press Enter

var1 dot kind underscore of question mark Integer

and press Enter

To do so, just assign a new value to it.

Let's do this by assigning a string value to variable var1.

var1=”hello”<< press Enter

var1 equal to within double quote hello

press Enter

var1.class<< press Enter

Type

var1 dot class

Now Press Enter

Converting variable types

Highlight to_s

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
  

The to _ s() method takes number base as an argument.

The conversion depends on this number base.

Go to the terminal

Lets clear the terminal first

Press Ctrl,l to clear the irb console

y=20<<press Enter

y equal to 20

and Press Enter

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

y.to_f<< press Enter

y dot to underscore f and

Press Enter

y.to_s<< press Enter

y dot to underscore s.and

Press Enter

y.to_s(2)<<press Enter

opening bracket 2 closing bracket and

press Enter

By changing the number base to 8 or 16.

Variable Scope

Scope defines where in a program a variable is accessible.

Ruby has four types of variable scope:

• Local
• Global
• Instance
• Class

Naming Convention

At the beginning of the variable name

Name Beginning With Variable Scope

$ A global variable

[a-z] or _ A local variable

@ An instance variable

@@ A class variable

[A-Z] A constant

$ represents global variable

Lower case letters and underscore represents a local variable

@ represents an instance variable

Two @@ represents a class variable

Upper case letters represents a constant

This brings us to the end of this Spoken Tutorial.let us summarise

Summary

• To declare a variable
  eg var1=10
• Changing variable type using to_f, to_s methods
• Different Variable scope

Assignment

Declare a variable and convert it to octal and hexadecimal form

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Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on this Mission is available at:

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This is Afrin Pinjari from IIT Bombay, signing off.

Thank you for watching.