Ruby

Ruby has four types of variable scope, 

Name Begins With	Variable Scope
$	A global variable
@	An instance variable
[a-z] or _	A local variable
[A-Z]	A constant
@@	A class variable

Detecting the Scope of a Ruby Variable

x = 10
=> 10
defined? x
=> "local-variable"

$x = 10
=> 10
defined? $x
=> "global-variable"

Ruby Class Variables

A class variable is a variable that is shared amongst all instances of a class.

Class variables must be initialized at creation time.

@@total = 0

Another way of thinking of thinking of class variables is as global variables within the context of a single class.

Ruby Instance Variables

Instance variables are similar to Class variables except that their values are local to specific instances of an object.

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