Ruby

Question 1

*.rb

Answer 1

Ruby code file extension

Question 2

irb

Answer 2

built-in Ruby function for running ruby code outside a ruby code file.

Question 3

#

Answer 3

ruby comment line

Question 4

snake_case

Answer 4

defining or initializing variables, methods, or files, should always be named using snake_case:
lower case lettering and separated words using underscore.

Question 5

constants

Answer 5

denoted by all uppercase letters

Question 6

CamelCase

Answer 6

convention for class names
Capitalize every word, no spaces

Question 7

Max line length

Answer 7

80 chars

Question 8

spaces around operators

Answer 8

use spaces around operators

• • except exponent (4**2), the slash in rational literals (1/48r), safe navigation (foo&.bar)
• • no spaces after ( and [, or before ] and )
• • use spaces around { and before }, except interpolated expressions have no spaces
• • no space after bang (!)
• • no space inside range literals (‘a’…‘z’)

Question 9

case when indents

Answer 9

case
when....
  puts....
when...
  puts...
else
  ....
end

Question 10

puts

Answer 10

display result to console, adding line return at the end
puts “This is test to display”
puts my_variable

Question 11

print

Answer 11

display result to console, with no trailing spaces or line feed
print “This is test to display”
print my_variable

Question 12

text

Answer 12

Single line comment

Question 13

=begin
text
more text
=end

Answer 13

multiline comment

Question 14

Float

Integer

Answer 14

Numeric data types

Question 15

\+
-
*
/
**
%

Answer 15

Common arithmetic operations

Question 16

variable.method

Answer 16

all variables in ruby are objects, and have methods available to them

Question 17

strings

Answer 17

delineated by single or double quotation marks

Question 18

true, false

Answer 18

Boolean values

Question 19

.upcase
.downcase
.

Answer 19

converts string to all uppercase or lowercase

Question 20

“your result is #{result}, congratulations”

Answer 20

string interpolation with variable

Question 21

gets.chomp

Answer 21

method for getting user input
gets is the method for retrieving input
chomp removes the new line that ruby automatically adds to a gets call

Question 22

if *test*
  do something
elsif *test*
  do something else
else
  do a third thing
end

Answer 22

if else conditional
else is required, any number of elsif statements allowed
requires end to stop

Question 23

!=

Answer 23

Not!

Question 24

||

Answer 24

or

Question 25

&&

Answer 25

and

Question 26

if condition
do something
end

-or-

expression if boolean

Answer 26

if conditional

Question 27

unless test
do something
end

-or-

do something unless boolean

Answer 27

unless statement

Question 28

string.include? “value”

Answer 28

returns true if value is in string

Question 29

string.gsub!(/value/, “new_value”

Answer 29

global substitution

updates string to replace value with new_value

Question 30

counter 
while counter not some value
  do something
  increment counter
end

Answer 30

while loop syntax

Question 31

counter
until counter evaluation
do something
end

Answer 31

Until loop syntax

Question 32

+=, -=, *=, /=

Answer 32

reassignment operators. return the calculated result to the variable
example: counter += 1, will increment counter variable by 1

Question 33

for counter in range
do something
end

Answer 33

for loop syntax

Question 34

counter
loop do
  execute something
  increment counter
  break
end

Answer 34

loop syntax.

do… end can be replaced with {..}

Question 35

break
or
break if test

Answer 35

ends loop iteration at break statement

Question 36

next if test

Answer 36

skips to following iteration

Question 37

object.each { |item| 
  # Do something 
}

Answer 37

each operator executes on each item in an array

{…} can be replaced with do…end, which is preferred with longer than 1 line statement

Question 38

num.times {execute something}

Answer 38

times loop

Question 39

string.split(“separator”)

Answer 39

converts string to array with designated separator

Question 40

hash = {“key”=> “value”, “key”=>”value, …}

Answer 40

Like an object in javascript

made up of keys and values

Question 41

Hash.new(default value)

Answer 41

creates empty hash
same as:
my_hash = {}
default value is optional. With no default, {} = nil

Question 42

hash.sort_by do |key,value|
count
end

Answer 42

sorts hash smallest to largest
cant be used with bang “sort_by!”
has to be multiline, not “ hash.sort_by { |key,value| count }

Question 43

Reusable section of code written to perform a specific task in a program

Answer 43

Method

similar to a function in other languages

Question 44

<=>

Answer 44

Combined comparison operator
compares two items. returns 1 if first > second, 0 if equal, -1 if second > first

array. sort! { |x,y| x<=>y } sorts descending
array. sort! { |x,y| y<=>x } sorts ascending

Question 45

string. to_sym

string. intern

Answer 45

converts string to symbol

Question 46

hash.select { |key,value| test}

Answer 46

Selects

Question 47

case string
  when x
    do x
  when y
    do y
end
-or-
case string
  when x then x 
  when y then y
end

Answer 47

case statement is effectively multiple if elsif statements

Question 48

boolean ? Do this if true: Do this if false

Answer 48

Ternary conditional expression

takes 3 arguments: boolean, expression to eval if true, and expression to eval if false

Question 49

||=

Answer 49

Conditional assignment operator.

Only assigns value if the variable != nil

Question 50

implicit return

Answer 50

If a method has no return statement, the last evaluated expression will be returned

Question 51

object.respond_to?(symbol)

Answer 51

tests whether an object will receive a method
e.g. [1, 2, 3].respond_to?(:push) returns true becasue an array can have push
[1, 2, 3].respond_to?(:to_sym) returns false because an array can’t be converted to symbol

Question 52

<

Answer 52

“The Shovel”, or the concatenation operator, can be used to add an element to the end of an array, text

[1,2,3] << 4
# ==> [1,2,3,4]

Question 53

x.floor

Answer 53

rounds down a number to closest whole below it

floor can also be achieved by x.to_i

Question 54

Proc.new { |x| execute someething }

Answer 54

a Proc is a block that can be reused
it’s called using the (&procname) syntax

proc’s can be called via argument [function(&procname)], or using procname.call

Question 55

numbers_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

strings_array = numbers_array.map(&:to_s)

puts strings_array

–> [“1”, “2”, “3”, “4”, “5”, “6”, “7”, “8”, “9”, “10”]

Answer 55

proc + symbol applied to convert array of integers to array of strings