Chapter 4

Question 1

true %>

Answer 1

build in rails function (stylesheet_link_tag) to include application.css for all media types (including computer screens and printers.

Question 2

helper functions

Answer 2

creation of new rails functions

Question 3

define a method full_title if no page title is defined (using provide on that page), then print out “Rails Tutorial Sample App”, otherwise add a | and precede it by the page title

Answer 3

module ApplicationHelper

# Returns the full title on a per-page basis
def full_title(page_title = '')
base_title = "Ruby on Rails Tutorial Sample App"
if page_title.empty?
base_title
else
page_title + " | " + base_title
end
end
end

Question 4

using full_title method, create a new title tag to use it:

Question 5

steps to make home page with no custom page title

Answer 5

update home page to remove the provide function. update the test assert to test this

Question 6

#

Answer 6

comments in ruby

Question 7

string literal

Answer 7

zero or more characters grouped in quotes

Question 8

concatenate two strings

Answer 8

“foo” + “bar”

“foobar”

Question 9

interpolate a string and define meaning

Answer 9

first_name = “sam”
“#{first_name} Erd”
“Sam Erd”. interpolation is using a placeholderto insert a certain variable

Question 10

printing a string

Answer 10

puts which appends a new line

Question 11

nil

Answer 11

literally nothing

Question 12

\n

Answer 12

new line

Question 13

difference between ‘’ and “”

Answer 13

nothing, there identical, except ruby wont interpolate into single-quoted strings

Question 14

is everything in ruby an object?

Answer 14

yes. even nil is an object.

Question 15

what is an object?

Answer 15

object is a model of something with behavior and functions and attributes. place to store data about an entity.

Question 16

empty?

Answer 16

method returns true or false

Question 17

if s is nil, return “nil”, else if s is empty, return “empty”, else if, s includes “foo”, return “foo”

Answer 17

if s.nil?
"nil"
elsif s.empty?
"empty"
elsif s.include?("foo")
"foo"
else
"lol"
end

Question 18

puts “empty” if x and y are empty, puts “one is empty” is x or y is empty, puts “x” if x is not empty
puts “xy” if neither x and y are empty

Answer 18

puts “empty” if x.empty? && y.empty?
puts “one is empty” if x.empty? || y.empty?
puts “x” if !x.empty?
puts “xy” if !x.empty? && y.empty?

Question 19

puts two variables if neither is empty

Answer 19

puts “#{x} #{y}” if !x.empty? && !y.empty?

Question 20

.to_s

Answer 20

convert virtually any object to a string.

Question 21

nil.to_s

Answer 21

””

Question 22

nil.empty?

Answer 22

error

Question 23

nil.to_s.empty?

Answer 23

true

Question 24

”“.nil?

Answer 24

false

Question 25

nil.nil?

Answer 25

true

Question 26

puts a string using interpolation unless its empty

Answer 26

puts “#{foo}” unless foo.empty?

Question 27

!!nil

Answer 27

false

Question 28

!!0

Answer 28

true

Question 29

def string_message(str = '')
returns whether string is empty or not. what is output for:
string_message("foo")
string_message("")
string_message

Answer 29

string is nonempty
string is empty
string is empty
its possible to leave out the argument entirely because the code contains a default argument, which in ths case is the empty string

Question 30

return string if its empty

Answer 30

return “empty” if str.empty?

Question 31

last return in a function is unnecessary why?

Answer 31

returned regardless of return keyword

Question 32

module ApplicationHelpter

Answer 32

gives us a way to package together related methods which can be then mixed in to Ruby classes using “include”

Question 33

“foo bar yo” split this string into an array

Answer 33

“foo bar yo”.split

[“foo”, “bar”, “yo”]

Question 34

split “fooxbarx” by the x’s

Answer 34

“fooxbarx”.split(“x”)

[“foo”, “bar”

Question 35

get first, second, last elenment of an element

Answer 35

a. first
a. second
a. last

Question 36

a.last == a[-1]

Answer 36

true

Question 37

x = a.length

Answer 37

length of a string or could be array

Question 38

a = [41, 8, 17]
empty
include 41
sort it
reverse the order
shuffle it

Answer 38

a. empty?
a. include?(41)
a. sort (can be used for strings too!)
a. reverse
a. shuffle

Question 39

a.sort!

Answer 39

actually changes to array a unlike a.sort which just outputs a sorted array

Question 40

push elements into array

Answer 40

x.push(6)

x

Question 41

a = [42, 8, “foo”]
a.join
join using comma

Answer 41

“428foo”
a.join(‘, ‘)
“42, 8, foo”

Question 42

0..9.to_a

Answer 42

undefined method for 9:fixnum

Question 43

(0..9).to_a

Answer 43

gives array from 0 to 9, 10 elements

Question 44

make a string array out of the words foo bar baz

and then show range of it

Answer 44

a = %w[foo bar baz]

a[0..2]

Question 45

a = (0..9).to_a

return array from index 1 up to last index

Answer 45

a[1..-1]

Question 46

range 1 through 5 and put our each number times 2

Answer 46

(1..5).each { |i| puts 2 * i}

or

(1..5).each do |i|
puts 2 * i
end

Question 47

(1..5).each { |i| puts i}

Answer 47

each method passes range to block. |i| block variable. executes for each value in the range

Question 48

puts “betelgeuse” three times

Answer 48

3.times {puts “betelgeuse” }

takes no variables

Question 49

(1..5).map { |i| i ** 2 }

Answer 49

[1, 4, 9, 16, 25] produces new array

Question 50

map out [a b c] into an array and change characters to uppercase or lower case

Answer 50

%w[a b c].map { |char| char.upcase(or char.downcase) }

Question 51

map A B C into array and lower case it using symbol

Answer 51

%w[A B C].map(&:downcase)

Question 52

test "should get home" do
  get :home
  assert_response :success
  assert_select "title", "Ruby on Rails Tutorial Sample App"
end

Answer 52

do keyword that the body of the test is a block. test method takes in a string argument and a block, and then executes the body of the block as part of running the test suite.

Question 53

user = {}

Answer 53

empty hash

Question 54

user[“first_name”] = “michael”

Answer 54

key “first_name”, value “michael”

Question 55

user[“first_name”]

Answer 55

returns value of key “first_name

Question 56

create hash user with first name vampie in one line

Answer 56

name = { “first_name” => “vampie” }

Question 57

in rails whats more common to use than strings as hask keys

Answer 57

symbols

Question 58

symbol

Answer 58

looks like string but prefixed with colon. :name symbols dont contain value or objects, like variables. used as consistent name in a code. compared to String objects, its more efficient to use symbols.

current_situation = "good" creates string object and stores in memory
current_situation = :good are only singe reference values only initialized once.

Question 59

create hash with symbols

Answer 59

user = { :name => “f”, :email => “at” }

Question 60

accessing undefined keys return what?

Answer 60

nil

Question 61

create hash with special hash symbol

Answer 61

user = { name: “f”, email: “at” }

Question 62

create nested hashes user with name and email

Answer 62

params[:user] = { name: “f”, email: “at” }

nested hashes are heavily used by rails

Question 63

create each do for hash

Answer 63

hash.each do |key, value|
puts “key: #{key.inspect} has value #{value.inspect}”
end

Question 64

inspect methdo

Answer 64

returns a string with a literal representation of the object

Question 65

puts (1..5).to_a

Answer 65

1
2
3
4
5

Question 66

puts (1..5).to_a.inspect

Answer 66

[1, 2, 3, 4, 5]

Question 67

puts :name, :name.inspect

Answer 67

name

:name

Question 68

puts “it\n”, “it\n”.inspect

Answer 68

it

“it\n”

Question 69

stylesheet_link_tag ‘application’, media: ‘all’,
‘data-turbolinks-track’ => true

why no parenthesis?

Answer 69

in ruby, they are optional. there would be a parenthesis around it

when hashes are the last arguments to a function, the parenthesis are optional

Question 70

stylesheet_link_tag ‘application’, media: ‘all’,
‘data-turbolinks-track’ => true
explain this now

Answer 70

calls the stylesheet_link_tag function with two arguments: a string, indicating the path to the stylesheet, and a hash with two elements, indicating the media type and telling Rails to use the turbolinks feature added in Rails 4.0.

data-track contains hyphens which are not allowed for symbols so we have to use the old syntax for it

Question 71

s = String.new(“foobar”)

Answer 71

constructor to create string

Question 72

a = Array.new([1, 2, 3])

Answer 72

array constructor

Question 73

h = Hash.new(0)

Answer 73

(hash constructor) sets all nonexistent keys to return 0 instead of nil

Question 74

s.class.superclass

Answer 74

string -> object -> basicObject -> nil

Question 75

create class Word with method palindrom? that returns if a string in reverse is equal to the string forward

Answer 75

class Word
def palindrome?(string)
string == string.reverse
end
end

Question 76

create palindrome method with class that inherits from string object

Answer 76

class Word

Question 77

how can we add palindrome? to string class

Answer 77

class String
create palindrome? method
end
now every string object has palindrome? method

Question 78

blank? method

Answer 78

specific to rails since its a rails extension

Question 79

controller = StaticPagesController.new

Answer 79

create controller object

Question 80

attr_accessor :name, :email

Answer 80

attr_accessor allows us to get and set @name and @email instance variables

Question 81

def initialize(attributes = {})
    @name  = attributes[:name]
    @email = attributes[:email]
  end

Answer 81

empty hash. will return nil if there is no :name key and for :email.

Question 82

def formatted_email
    "#{@name} "
  end

Answer 82

returns name

Question 83

require ‘./example_user’

Answer 83

include ruby code into your session or code from a file in the current directory

Question 84

we will see starting in chapter 7 that initializing objects using hash arguments, a technique known as mass assignment, is common in rails

Answer 84

true