Chapter 4

Question 1

true %>

Answer 1

includes application.css for all media types(computer screens and printers ect). to rails developer, this line looks simple.

Question 2

define full_title helper method. returns base title if no page title is defined

Answer 2

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 3

you created full_title helper method. change the line in application.html.erb to use this

Answer 3

title>

Question 4

interpolation

Answer 4

embed expressions into strings (even logic). process of inserting the result of an expression into a string literal (evaluate expression and insert)

Question 5

comments in rails

Answer 5

lskdjfkd

Question 6

puts

Answer 6

most commonely used ruby function to print a string. returns nil for nothing

Question 7

’#{foo} bar’ output

Answer 7

”#{foo} bar”. ruby wont interpolate single quotes

Question 8

usefulness of single quote literals

Answer 8

show exactly the characters you type

Question 9

“foobar”.length

Answer 9

6

Question 10

“foobar”.empty?

Answer 10

false

Question 11

create if else statements: if s is nil, else if s is empty, else if s include “foo”

Answer 11

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

Question 12

x = “foo”
y = “”
print out both if both are empty. print one if one of them is empty
print none if x is not empty

Answer 12

puts “both” if x.empty? && y.empty?
puts “one” if x.empty || y.empty?
puts
“x not empty” if !x.empty?

Question 13

nil.to_s

Answer 13

””

Question 14

nil.empty?

Answer 14

undefined method nil for nil:NilClass

Question 15

“foo”.nil?

Answer 15

false

Question 16

”“.nil?

Answer 16

false

Question 17

nil.nil?

Answer 17

true

Question 18

create similar statement to puts “x” if !x.empty? with “unless”

Answer 18

puts “x” unless x.empty?

Question 19

def string_message(str = ‘ ‘). explain str

Answer 19

default argument str. you can call this method by saying “string_message” without arguments

Question 20

“foo bar bax”.split

Answer 20

[“foo”, “bar”, “bax”]

Question 21

“fooxbarxbazx”.split(‘x’)

Answer 21

[“foo”, “bar”, “baz]

Question 22

a = [42, 8, 17]

a[-1]

Answer 22

17

Question 23

name the methods you know you can do with:

x = “hello”

Answer 23

.length
.empty?
.nil?
.include?("foo")
.split
.split("l")

Question 24

name the methods you know you can do with:

a = [5, 8, 6]

Answer 24

a[0] 5
a[-1] = 6
a.first
a.last
a.length
a.empty?
a.include?(42)
a.reverse
a.shuffle
a.sort! (changes a)
a.sort
a.push(6) [5, 8, 6, 6]
a

Question 25

create array with integers 0 through 9

Answer 25

0..9.to_a

Question 26

create array with all letters in alphabet

Answer 26

(‘a’..’z’).to_a

Question 27

turn “hello world my name is” into an array without split

Answer 27

a = %w[hello world my name is]

Question 28

explain:

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

Answer 28

calls the each method on the range (1..5) and passes it the block { |i| puts 2*i }. |i| is a block variable. each method can handle a block with a single variable and executes the block each value in the range

Question 29

when to use .each {} and .each do || end

Answer 29

.each {} for short one line code

.each do |i| end for multiple line

Question 30

range methods for:

1..5

Answer 30

.to_a
.each { |i| puts i}
.each do |i| puts i end
.map { |i| i**2} [1, 4, 9, 16, 25]

Question 31

test “should get home” do
get :home
assert_response :success
assert_select “title”, “ruby on rails”

Answer 31

body of the test is a block (from the keyword “do”).

and executes the block

Question 32

create array with all letters in alphabet and shuffle it and take first 8 elements and join them together

Answer 32

(‘a’..’z’).to_a.shuffle[0..7].join

Question 33

hash define:

Answer 33

different storage format that arrays. objects within hash are given a key that points to them. (if order matters, use arrays)

Question 34

create empty hash

and add a key/value pair to it

Answer 34

user = {}
user["first_name"] = "yolo"

Question 35

define a hash with multiple key/value pairs in one line

Answer 35

user = {“first” => “yolo”, “last” => “lolo” }

Question 36

Symbols (important concept)

Answer 36

abstract references. symbols dont contain values or objects. they are used as consistent name within code.

Question 37

create hash with symbol and symbol from special case which ruby supports now

Answer 37

h1 = {:name => “michael”}
h2 = {name: “michael”}
h1 == h2
true

Question 38

create a nested hash and access the value within

Answer 38

params = {}
params[:user] = { name: “test”, email: “@.com”}
params[:user][name:]

Question 39

flash is a hash. iterate through it

Answer 39

flash.each do |key, value|

puts “key #{key.inspect} has value #{value.inspect}. .inspect returns string with a literal representation of the object

Question 40

puts “it worked”, “it worked”.inspect

Answer 40

it worked

“it worked”

Question 41

.insect relation to p

Answer 41

inspect to print an object is common enough that theres a shortcut for it, the p function

Question 42

stylesheet_link_tag ‘application’, media: ‘all’, ‘data-turbolinks-track’ => true (important to know)

Answer 42

in ruby, functions can have parentheses. but they are also optional
stylesheet_link_tag(…) same thing as the question. also the media argument looks like a hash. when hashes are the last arguments in a function, they curly braces are optional.
( {media: ‘all’, ‘data-turbolinks-track’ => true} is the same thing (we dont say data-turbolinks-track: because hyphens cant be used with symbols

Question 43

“fooar”.class

Answer 43

string

Question 44

s = String.new(“foobar”)

Answer 44

constructor for string

Question 45

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

Answer 45

array constructor

Question 46

h = Hash.new

Answer 46

{}

h[:foo]

Question 47

h = Hash.new(0)

Answer 47

{}
h[:foo]
0

Question 48

string

Answer 48

inheritance

Question 49

create a class called Word with a method called palindrome? which returns true if the words are the same in reverse

Answer 49

class Word
def palindrome?(string)
return string == string.reverse
end
end
w = Word.new
w.plaindrome?("level")

Question 50

create palindrome? with class Word inherating from string

Answer 50

class Word

Question 51

are ruby classes like String open to add more methods to them?

Answer 51

yes, i could create class String and add palindrome? method to it which will work for all string objects

Question 52

use .blank? and .empty? methods

Answer 52

” “.empty? false

“ “.blank? true (method provided with rails)

Question 53

create controller in ruby console for the controller we created

Answer 53

controller = StaticPagesController.new

constroller. class.superclass
controller. home

Question 54

class User
attr_accessor :name, :email (explain)

Answer 54

creates attribtue accessor.
this creates “getter” and “setter” methods that allow us to retrieve and assign @name and @email instance variables. (example.name = “example user’ and example.name are examples of the getter and setter only bcause of the attr_accessor)

Question 55

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

Answer 55

default value is empty hash which defines a user and email with no values (nil).

Question 56

require ‘./example_user’

Answer 56

this is how you load the example_user code into the console. the . is unix for “current directory”.

Question 57

you created User with name and email instance variables. create it

Answer 57

user = User.new(name: “name”, email: “email);

Question 58

blocks in ruby

Answer 58

flexible construct that allow natural iteration over enumerable data structures.