Variables

Question 1

Variable Scope

Answer 1

Determines where in a program a variable is available for use. Is defined by where the variable is initialized or created. Is defined by a method definition or a block

Question 2

Rule one of variable scope

Answer 2

Inner scope can access variables initialized in an outer scope, but not vice versa.

Question 3

Variables

Answer 3

used to store information to be referenced and manipulated in a computer program

Question 4

assignment operator

Answer 4

= (assigns value)

Question 5

equality operator

Answer 5

== (checks if two things are equal)

Question 6

block

Answer 6

piece of code that follows a method’s invocation, delimited by either curly braces {} or do/end

Question 7

scope.rb

a = 5 # variable is initialized in the outer scope

3.times do |n| # method invocation with a block
a = 3 # is a accessible here, in an inner scope?
end

puts a

What is the value of a when it is printed to the screen?

Answer 7

The value of a is 3. This is because a is available to the inner scope created by 3.times do … end, which allowed the code to re-assign the value of a.

Question 8

Convert the following code into a one liner:
# scope.rb

a = 5 # variable is initialized in the outer scope

3.times do |n| # method invocation with a block
a = 3
end

puts a

Answer 8

3.times { |n| a = 3 }

Question 9

Constants

Answer 9

• declared by capitalizing every letter in the variable’s name.
• used for storing data that never needs to change

Question 10

Global Variables

Answer 10

declared by starting the variable name with the dollar sign ($).
-these variables are available throughout your entire app, overriding all scope boundaries.

Question 11

Class variables

Answer 11

declared by starting the variable name with two @@ signs.
-accessible by instances of class as well as the class itself.

Question 12

Instance variables

Answer 12

• declared by starting the variable name with one @ sign.

- available throughout the current instance of the parent class.