Ruby Intro/Variables

Question 1

what is a variable?

what are its two parts?

Answer 1

“a container that holds info”/”a way to label data with a descriptive name”/”a variable’s purpose is to name and store data in memory”

a name and a value

x = true
(x is the name, true is the value)

*choose a variable’s name carefully. make sure it’s descriptive and easily understood by you and other programmers)

Question 2

irb :001 > a = 4
=> 4
irb :002 > b = a
=> 4
irb :003 > a = 7
=> 7
----------------
What is the value of b now?

Answer 2

It’s still 4 because what was the value of “a” when you linked “b” to it

“variables point to value in memory”

Question 3

What does the “gets” method do?

Answer 3

It allows the user to input data/It gets a sting from a user

“gets” pauses the program and waits for the user to type in some information and hit the enter key

Question 4

What does “chomp” do?

Answer 4

it removes the newline character ( \n ) that automatically appears at the end of a string when “gets” is used

Question 5

What is a block?

Answer 5

a piece of code that follows a method’s invocation

You can use { } if all the code fits on one line:

total = 0
[1, 2, 3].each { |number| total += number }
puts total

OR……

“do/end” if the code takes up two or more lines:

total = 0
[1, 2, 3].each do |number|
  total += number
end
puts total

Question 6

If you see some code in ruby, how do you know if it’s a block?

Answer 6

the code follows the invocation of a method
( .times, .split, etc)

This is NOT a block:

for i in arr do
a = 5
end
puts a

Why? the “do/end” part doesn’t follow the invocation of a method. also, “a” is accessible in the program b/c “a=5” was not created in the inner scope of a block. in other words, no “inner scope” was created

Question 7

True or false?

Variables set inside of a block or a method are accessible outside of that block or method?

Answer 7

false

Question 8

True or false?

Code created in a block or method can access a variable initialized outside of that block or method.

Answer 8

true

Question 9

Is this a block? Why or why not?

3.times { |n| a = 3 }

Answer 9

yes, because the code inside { } follows the invocation of a method (.times)

Question 10

What are the five types of variables?
1-  c\_\_\_\_\_\_ts
2- g\_\_\_\_\_\_l  variables
3- c\_\_\_\_\_s  variables
4- i\_\_\_\_\_\_e  variables 
5- l\_\_\_\_\_\_l  variables

Which type is the most common

Answer 10

constants (named in ALL_CAPS)

global variables (name starts with $. not used very often)

class variables (name starts with @@ )

instance variable (name starts with @ )

local variables (named with snake_case )
-----------

local variables are the most commonly used in ruby

Question 11

What does this mean?

x += 1

Answer 11

It’s shorthand for “x = x + 1”

this math operation is called “reassignment”

Question 12

Are there any problems here?

y = 0
3.times do
  y += 1
  x = y
end
puts x

Answer 12

Yes.

x was initialized inside the block, so it is not visible to the outer scope

(inner scope vs. outer scope)