Ruby

Question 1

What are some basic classes?

Answer 1

Fixnum
String
Array
Hash

Question 2

How to get user input?

Answer 2

input = gets.chomp // chomp removes \n

Question 3

How to convert string to int and int to string?

Answer 3

string.to_i and int.to_s

Question 4

Method and constructor format?

Answer 4

def initialize    // a constructor w/o params
  // code
end

def initialize(name, age)    // a constructor w params
  // code
end

Question 5

A class with class and instance variables? Also define a sub class?

Answer 5

class MyClass
  @instanceVariable
  @@classVariable

def myMethod
localVariable = 2
end
end

class MySubClass

Question 6

what is the spaceship operator?

Answer 6

a b

// resutls in
a  b   = 1

Question 7

Array Syntax?

Answer 7

animals = Array.new 
animals = ["bear", "dog", "cat"]
animals[0]  // bear
animals[0] = 1  
animals[0] // 1

arr[:slot1, :slot2, :slot3]
:slot1 // arr[0]

Question 8

Iterate over array?

Answer 8

arr.each { |x| puts x }

Question 9

Null in Ruby?

Answer 9

nil

Question 10

What is a block and are they first class citizens?

Answer 10

A function w/o a name.

3.times { |x| puts x}
block-> |—————|

A block cannot be assigned to a variable as it is not a first class citizen. So one must use a proc:

b = Proc.new { |x| puts x }
b.call(x)

Question 11

How to use yield?

Answer 11

def test
  yield 5
end
test { |x| puts x}   // called when yield is called (also works w/o param)

Question 12

A ruby while loop?

Answer 12

i = 0

while i

Question 13

Define Ruby?

Answer 13

Object orientated
Interpreted
Dynamically typed
Strongly typed for the most part

Question 14

How to evaluate a string before returning it?

Answer 14

One quote interprets string literraly
Double quotes evals string

x = 5
puts “Number: #{x}” // Number: 5
puts ‘Number: #{x}’ // Number: #{x}

Question 15

Method parameter optional value with default value?

Answer 15

def myMethod(req, optional=1)
  // code
end

Question 16

Ruby associative array (hash)?

Answer 16

h = Hash.new
h = { "a" => 100, "b" => 200 }

or

h { :a => 100, :b => 200 } // more efficient as a new string need not be created.

Question 17

How to create setters and getters?

Answer 17

class MyClass
attr :name, :age // getters
attr_accessor :name, :age // setters

Question 18

Arrays can act as stacks?

Answer 18

a. push(3) // adds 3 to end of array

a. pop // removes first elems

Question 19

Multidimensional arrays?

Answer 19

a = [[1,2,3], [4,5,6]]

a[0][0] // 1