Chapter 6

Question 1

default data structure for a data model

Answer 1

model M in MVC.

Question 2

Model

Answer 2

rails solution to use a database for long-term data storage

Question 3

active record

Answer 3

default library for interacting with the database

Question 4

benefit of active record

Answer 4

comes with host of methods for creating, saving, and finding data objects without having to use SQL used by relational databases.

Question 5

migration

Answer 5

allow data definitions to be written in pure ruby, without having to learn SQL language. way to alter the structure of the database incrementally, so our data model can adapt to changing requirements

Question 6

goals of a model

Answer 6

create model for users that wont disappear after creating them

Question 7

why dont we need to identify attributes explicitly when modelling users.

Answer 7

rails uses relational database by default, which composed of data rows, where each row has columns of data attributes. active record will figure out the User object attributes fro us from the database

Question 8

why we dont need to include id as parameter for user

Answer 8

it is created by rails for use as the primary key in the database

Question 9

command for making a model with name and email attributes

Answer 9

rails generate model User name:string email:string

Question 10

model name are singular

Answer 10

true

Question 11

db/migrate/[timestamp]_create_user.rb

Answer 11

timestamp based on when the migration was generated

Question 12

def change
create_table :users do |t|
t.string :name
t.string :email

  t.timestamps null: false
end

Answer 12

change method that determines the change to be made to the database. rails method called create_table to create a table in the database for storing users. create_table accepts a block with one block variable called “t”.inside block, uses the t object to create name and email columns.

Question 13

create_table :users do |t|. why is users plural

Answer 13

even though the model is singular, rails follows a linguistic convention. a database table consists of many users.

Question 14

t.timestamps null:false

Answer 14

creates two magic columns called created_at and updated_at, which are timestamps that automatically record when a given user is created and updated.

Question 15

bundle exec rake db:migrate

Answer 15

updates the database with our new users data model. creates a file called db/development.sqlite3, which is an sqlite database.

Question 16

how to see development.sqlite3

Answer 16

with DB Browser for SQLite. download it, then download development.sqlite3 and open to view it

Question 17

migrate down and undo a migration

Answer 17

bundle exec rake db:rollback

Question 18

class User

Answer 18

User inherits from ActiveRecord::Base so that the User model automatically has all the functionality of the ActiveRecord::Base class.

Question 19

opening up console in a sandbox

Answer 19

rails console –sandbox. any modifications you make will be rolled back on exit.

Question 20

User.new for models

Answer 20

do not have to ‘require’ for models. rails console automatically loads the rails environment which includes the model.

Question 21

create new user with name and email

Answer 21

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

Question 22

user = User.new….

user.valid?

Answer 22

boolean valid? returns if object is valid

Question 23

save object to database

Answer 23

user.save. returns true if it succeeds

Question 24

user.updated_at

Answer 24

get time user was updated

Question 25

create new user in database with one line and store in variable

Answer 25

foo = User.create(name: “name”, email: “email”)

Question 26

destroy object

Answer 26

foo.destroy. object still exists in memory if you run foo. we need to learn about Active Record to fix this

Question 27

User.find(1)

Answer 27

find user with id 1. ActiveRecord method for finding objects

Question 28

User.find(2) (when we deleated 2)

Answer 28

raise exception saying couldnt find user with id = 2

Question 29

find user with email

Answer 29

User.find_by(email: “email”)

ActiveRecord method for finding user with specific attributes.

Question 30

get first user in database

Answer 30

User.first (A.R method)

Question 31

return all users

Answer 31

User.all (A.R method) returns all the users in the database as an object of class ActiveRecord::Relation which is effectively an array

Question 32

update user object email

Answer 32

user. email = “newEmail”

user. save

Question 33

user.email
“email”
user.email = “newEmail”
user.reload.email gives what?

Answer 33

“email”. without saving, reloads object based in the database information

Question 34

update user with activerecord method

Answer 34

user.update_attributes(name: “newName”, email: “canAddMoreAttributes”) (automatically updates the database and changes the updated_at timestamp) also user.update_attribute(:name, “name”) updates one attribute. if one of the update_attributes fails, then it all fails and wont update anything

Question 35

command to test just the model tests

Answer 35

bundle exec rake test:models

Question 36

test for validity for user object in user_test.rb

Answer 36

test “should be valid” do
assert @user.valid?
end