Chapter 4 Flashcards by Saweel Ahmed

true %>

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

How well did you know this?

Not at all

Perfectly

helper functions

creation of new rails functions

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

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

How well did you know this?

Not at all

Perfectly

steps to make home page with no custom page title

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

How well did you know this?

Not at all

Perfectly

comments in ruby

How well did you know this?

Not at all

Perfectly

string literal

zero or more characters grouped in quotes

How well did you know this?

Not at all

Perfectly

concatenate two strings

“foo” + “bar”

“foobar”

How well did you know this?

Not at all

Perfectly

interpolate a string and define meaning

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

How well did you know this?

Not at all

Perfectly

printing a string

puts which appends a new line

How well did you know this?

Not at all

Perfectly

nil

literally nothing

How well did you know this?

Not at all

Perfectly

new line

How well did you know this?

Not at all

Perfectly

difference between ‘’ and “”

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

How well did you know this?

Not at all

Perfectly

is everything in ruby an object?

yes. even nil is an object.

How well did you know this?

Not at all

Perfectly

what is an object?

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

How well did you know this?

Not at all

Perfectly

empty?

method returns true or false

How well did you know this?

Not at all

Perfectly

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

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

How well did you know this?

Not at all

Perfectly

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

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?

How well did you know this?

Not at all

Perfectly

puts two variables if neither is empty

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

How well did you know this?

Not at all

Perfectly

.to_s

convert virtually any object to a string.

How well did you know this?

Not at all

Perfectly

nil.to_s

””

How well did you know this?

Not at all

Perfectly

nil.empty?

error

How well did you know this?

Not at all

Perfectly

nil.to_s.empty?

true

How well did you know this?

Not at all

Perfectly

”“.nil?

false

How well did you know this?

Not at all

Perfectly

nil.nil?

true

puts a string using interpolation unless its empty

puts "#{foo}" unless foo.empty?

!!nil

false

!!0

true

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

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

return string if its empty

return "empty" if str.empty?

last return in a function is unnecessary why?

returned regardless of return keyword

module ApplicationHelpter

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

"foo bar yo" split this string into an array

"foo bar yo".split | ["foo", "bar", "yo"]

split "fooxbarx" by the x's

"fooxbarx".split("x") | ["foo", "bar"

get first, second, last elenment of an element

a. first a. second a. last

a.last == a[-1]

true

x = a.length

length of a string or could be array

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

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

a.sort!

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

push elements into array

x.push(6) | x

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

"428foo" a.join(', ') "42, 8, foo"

0..9.to_a

undefined method for 9:fixnum

(0..9).to_a

gives array from 0 to 9, 10 elements

make a string array out of the words foo bar baz | and then show range of it

a = %w[foo bar baz] | a[0..2]

a = (0..9).to_a | return array from index 1 up to last index

a[1..-1]

range 1 through 5 and put our each number times 2

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

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

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

puts "betelgeuse" three times

3.times {puts "betelgeuse" } | takes no variables

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

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

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

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

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

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

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

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.

user = {}

empty hash

user["first_name"] = "michael"

key "first_name", value "michael"

user["first_name"]

returns value of key "first_name

create hash user with first name vampie in one line

name = { "first_name" => "vampie" }

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

symbols

symbol

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. ```

create hash with symbols

user = { :name => "f", :email => "at" }

accessing undefined keys return what?

nil

create hash with special hash symbol

user = { name: "f", email: "at" }

create nested hashes user with name and email

params[:user] = { name: "f", email: "at" } | nested hashes are heavily used by rails

create each do for hash

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

inspect methdo

returns a string with a literal representation of the object

puts (1..5).to_a

``` 1 2 3 4 5 ```

puts (1..5).to_a.inspect

[1, 2, 3, 4, 5]

puts :name, :name.inspect

name | :name

puts "it\n", "it\n".inspect

it | "it\n"

stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true why no parenthesis?

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

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

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

s = String.new("foobar")

constructor to create string

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

array constructor

h = Hash.new(0)

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

s.class.superclass

string -> object -> basicObject -> nil

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

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

create palindrome method with class that inherits from string object

class Word

how can we add palindrome? to string class

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

blank? method

specific to rails since its a rails extension

controller = StaticPagesController.new

create controller object

attr_accessor :name, :email

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

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

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

``` def formatted_email "#{@name} " end ```

returns name

require './example_user'

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

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

true