Ruby

Question 1

What is this operator < = > and what does it do?

Answer 1

The combined comparison operator (ie, Spaceship operator:
Returns 0 if the first operand equals the second operand;
Returns 1 if the first operand is greater than the second;
Returns -1 if the first operand is less than the second operand.

Question 2

How would you compare and sort an array into an ascending order or items based on their size

Answer 2

arr.sort { |a ,b | a.size < = > b.size }

Use the following to sort in descending order

arr.sort { |a, b | a.size < = > b.size }

Question 3

What method would we use to sort an array that has items with lower and upper case ie, normal spaceship sort comparison operator won’t work correctly.

Answer 3

arr.sort!{|a, b| a.casecmp(b)}

Question 4

What is the notation to convert a string into an array

Answer 4

str = w% { convert a string into an array }

=> [“convert”, “a”, “string”, “into”, “an”, “array”]

Question 5

What is the methods to add an item from the end of an array?

Answer 5

#push adds on the end of an array. It modifies the array
or << shovel operator

arr = {1, 2, 3, 4]
arr.push( 555)

=> [1, 2, 3, 4, 555]

Question 6

What is the method to remove an item from the end of an array?

Answer 6

pop removes the last item from an array. it modifies the array

arr= [1, 2, 3, 4, 555]
arr.pop

=>[1, 2, 3, 4]

Question 7

What is the method to take off the first item from the following array?

arr = [1, 2, 3]

Answer 7

shift removes the first item from an array and modifies the array.

arr = [ 1, 2, 3]
arr.shift

=> [2, 3]

NB: #first gives the first item but doesn’t remove it ie, like arr [0]

Question 8

How do you add an item onto the front of an array?

Answer 8

unshift adds an item onto the front of an arry and modifies the array

arr = [1, 2, 3]
arr.unshift (999)

=> [999, 1, 2, 3 ]

Question 9

How do you delete an item from an array?

Answer 9

delete_at (index position)

arr = [ 1, 2, 3, 4 ]
delete_at ( 1 )

=> [ 1, 3, 4 ]

Note: if deleting items inside a loop it will change the index order.

Question 10

How do you convert an Array into a String?

Answer 10

use #join and pass in anything you want in between each element (the “separator”)

[ “he”, “llo”]. join

=> [ “hello” ]

Question 11

How do you break a string into pieces to create an array of substrings

Answer 11

Use #split

list = “eggs, milk, cheese and crackers”

list.split (“, “)
=> [“eggs”, “milk”, “cheese and crackers”]

list.split( “” ) or list.split ( // )
=> => [“e”, “g”, “g”, “s”, “,”, “ “, “m”, “i”, “l”, “k”, “,”, “ “, “c”, “h”, “e”, “e”, “s”, “e”, “ “, “a”, “n”, “d”, “ “, “c”, “r”, “a”, “c”, “k”, “e”, “r”, “s”]

Question 12

How do you search within and replace items within strings?

Answer 12

Use RegExp # gsub(pattern, replace_with_this)

> “hello”.gsub( “l”, “r” )

=> “herro”

Question 13

What methods could you use to iterate through a string and when would you use each method?

Answer 13

scan is used to iterate through a string matching the pattern (which may be a Regexp or a String). For each match, a result is generated and either added to the result array or passed to the block.

Use either #scan or #match

eg. Use a regex to match each individual character and return an array of the characters.

“some string”.scan( /. / )
=> [”s”, “o”, “m”, “e”, “ “, “s”, “t”, “r”, “i”, “n”, “g” ]

Question 14

How do you create an object in Ruby? Give an example of the creation of an object.

Answer 14

class MyClass
end

my_obj = MyClass.new

We crteate an object by defining a class and instantiating it using the .new method to create an instance, also known as an object.

Question 15

What is a module and what is its purpose?

Answer 15

A module allows us to group reusable code into one place. We use modules in our classes by using the “include” reserve word, followed by the module name.

module Study
end

class MyClass
include Study
end

my_obj = MyClass.new

Question 16

What are getters & setters?

Write out the getter & setter methods based off this shortcut version

attr_accessor :name, :height

Answer 16

Getters allow us to retrieve the state of an object.
Setters allow us to change the state of an object

def name
@name
end

def name=(new_name)
  @name = new_name
end

def height
@height
end

def height=(new_height)
  @height = new_height
end