Basics

Question 1

What is the request/response cycle?

Answer 1

The browser makes a request for the URL http://localhost:3000

The request hits the Rails router in config/routes.rb.

The router recognizes the URL and sends the request to the controller.

The controller receives the request and processes it.

The controller passes the request to the view.

The view renders the page as HTML.

The controller sends the HTML back to the browser for you to see.

Question 2

How do you make a controller?

Answer 2

rails g controller Name

Question 3

What is the workflow when making a rails app?

Answer 3

1) Generate a new rails app = rails new App_name
2) Generate a controller and add an action = rails g controller action
3) Create a route that maps a URL to a controller action
4) Create a view with HTML and CSS
5) Check it in the localhost with rails s

Question 4

How do the model and database fit into the request/response cycle?

Answer 4

When the controller action receives the request it send for the data to the model which in turn brings the data from the database and sends it back to the action.

Question 5

How do you create a model?

Answer 5

1) rails g model Name title:string description:text price:integer
2) run rails db:migrate
3) rails db:seed

Question 6

What does the model do?

Answer 6

It represents a table in the database

Question 7

What is a migration?

Answer 7

A migration is a way to update the database.

Question 8

What does the migration file contain?

Answer 8

1) It contains the change method which tells rails what change to make in the database
2) Inside the change method, we have the create_table method which creates a new table in the database for storing.
3) Inside the create table we have a title which creates a string and so on.
4) We also have the timestamps which automatically creates a created_at and updated_at

Question 9

What does rails db:seed do?

Answer 9

The command seeds the database with sample data from db/seeds.rb.

Question 10

What is the gemfile

Answer 10

The gemfile contains all the gems that your app uses.

With the source on the top that are housed in rubygems.org]

Question 11

What is bundle install?

Answer 11

Bundle goes to the source and brings the gems that you have in your gemfile and then installs them

Question 12

How is the gemfile grouped?

Answer 12

group development
group development test
group production
you place the gems depending on which environment you are using

Question 13

What is the gemfile.lock?

Answer 13

The bundler creates the gemfile.lock adds the dependencies that are needed. Never update this manually.

Question 14

What is the database.yml?

Answer 14

It says what databased are used and in what environment

Question 15

What are migrations?

Answer 15

files that we use to create or update databases.

Question 16

What is a class?

Answer 16

A collection of methods or functionality

Question 17

What is snake case?

Answer 17

snake_case.rb

All file names should be in snake case

Question 18

What is a CamelCase

Answer 18

All class names should be CamelCase
ApplicationController

Question 19

What is an action?

Answer 19

An action is a fancy name for a method.

Question 20

What is a view?

Answer 20

A view is everything you see in your browser.

Question 21

What does erb stand for?

Answer 21

embedded ruby all html files in rails are called name.html.erb

Question 22

What is the application.html.erb file?

Answer 22

The application.html.erb file is our wrapper file, that means that all of our view files are a part of that file. All files are displayed through that file.

Question 23

What is the inside the application.html.erb file?

Answer 23

This is where all your views show up from the other views.

Question 24

What is the naming convention for the controller files?

Answer 24

Controller file names need to be snake_case

Question 25

What do you need if you want a view from a controller?

Answer 25

You need to have a folder with the controller name under views if you want to have views. views/pages/filename

Question 26

What do you need if you want the views to create a view?

Answer 26

You need a action(method) defined and a html.erb file added to it under the views.

Question 27

How do you write a route?

Answer 27

get ‘/thispage’, to: ‘controller#action’

Get the route and send it to a controller with a action(method)

Question 28

What is the naming convention for model names?

Answer 28

A model name should be singular Model model.rb

Question 29

What is the naming convention for table names?

Answer 29

Tables should be in plural beacuse we have a lot of tables. tabels table

Question 30

What is the naming convention for controller names?

Answer 30

They should be in plural todos_controller.rb

Question 31

How do you create a migration file?

Answer 31

First you need to have a data model (model file)

rails generate migration create_todos

Question 32

How do you run a migration?

Answer 32

rails db:migrate

Question 33

Why do you run a migration file?

Answer 33

To create a table and actually impact the database i need to run a migration.

Question 34

How do you interact with the database?

Answer 34

You interact with the database with rails console.

Question 35

How do you create a database object?

Answer 35

In rails console
Initiate a new object
save the object

Question 36

What are the steps to make a new object in the database?

Answer 36

1) object = Class.new(name: "something", description: "else")
2 object.save
The class is the model name

Question 37

How do you see what is saved in the database?

Answer 37

ClassName.all

Question 38

What does the .create do in the database?

Answer 38

the .create will impact the database as long as there are no errors. you do not need to use.new and .save

Question 39

How do you find a object with a known id in the database?

Answer 39

some_variable_name = Class.find idnumber
example:
todo1 = Todo.find 2

Question 40

How do I update a object in a database from the console?

Answer 40

1) variable_name.what_you_want_to_change = “Changes”
2) variable_name.save

example
todo1.description = “eat something”

Question 41

How do I delete a object in the console?

Answer 41

1) variable_name = Class.last
2) varible_name.destroy

example
todo2 = Todo.last
todo2.destroy

Question 42

How do I make sure that there are no empty objects in the database?

Answer 42

You add

validates :name(or other), presence: true in the model class

Question 43

How do I see the error messages from rails console?

Answer 43

variablename.errors.any?
and
variablename.errors.full_messages

Question 44

How do you get all the CRUD routes?

Answer 44

with adding resources :classname in the route

Question 45

What is the purpose of the rails router?

Answer 45

It has two puorposes

1) Send a URL request to the right controller
2) Generate paths and URLS to avoid hardcoding strings in the views.

Question 46

How do you connect a URL to code in the rails routes?

Answer 46

If the incoming request is
GET /patient/17

This means that your route should be

get ‘/patient/:id, to ‘patient#show’

In plain english
get the route from patient id and send it to the patient controller and the show action(method)

Question 47

How do you generate a path or url from the code?

Answer 47

If you have this code in the controller:
@patient = Patient.find(17)

And this code in the view:

Then you type this in the route:
get ‘/patients/:id’, to: ‘patients#show’, as: ‘patient’

Question 48

What is resource routing?

Answer 48

Resource routing is when you declare all the crud functions routes for a controller with a single line of code.

Question 49

How do you use resource routing?

Answer 49

you type:

resources :controllername

Question 50

How can you have resources for multiple controllers?

Answer 50

by typing them after the first controller:

resources :photos, :books, :videos

Question 51

What is flash’?

Answer 51

Flash is essentially a hash which I can add messages and then display the messages.

Question 52

How do you find a object from a class?

Answer 52

@instance_variable = Class.find(params[:id])

Question 53

What is the preferred way to iterate in Ruby?

Answer 53

It is by using the .each method.

Question 54

How do you add links to the view?

Answer 54

with the _path method

you write :

you find the prefix in rails routes

Question 55

What are partials?

Answer 55

Partials allow you to organize and reuse your code in your rails application. It’s a way to keep your code DRY

Question 56

How to you create partials?

Answer 56

you create partials in the folder you need with the _partialname.html.erb

Question 57

How do you insert a partial in your code?

Answer 57

note:
you only need the folder if the partial is in another folder.
no _ in the beginning of the partial name nor a format name like html.erb in the end.

Question 58

How do you test if the routes you created work?

Answer 58

You type rails routes in the terminal and see if they are displaying in the terminal.

Question 59

How do you install bootstrap in rails?

Answer 59

You add the gem bootstrap
1) sass to your Gemfile
2) run bundle
3) add //= require bootstrap-sprockets under require jquery
4) create a new css.scss file under stylesheets.
5) In the scss file add
@import “bootstrap-sprocets’;
@import “bootstrap”;
Check if the gem has been properly installed by seeing if the font has changed

Question 60

What are relational databases?

Answer 60

It is a database structure based on rows and columns and their relationship

Question 61

What is SQL?

Answer 61

It stands for structured Queryt Language and is the language used to manage and maintain databases.

Question 62

What is Active Record?

Answer 62

Active record lets us manage databases without using SQL in Rails. Active Record takes ruby code and translates it to SQL

Question 63

What is RDBMS?

Answer 63

Relational Database Management System

such as MS SQL, Oracle, MySQL

Question 64

How is data stored in a database?

Answer 64

The data is stored in objects called tables.

Question 65

How are database tables structured?

Answer 65

They are structured in rows and columns

Question 66

What is a record?

Answer 66

A record is another name for a row (horizontal)

Question 67

What are SQL statements?

Answer 67

All actions you can perform to a database are done with SQL stetements

SELECT * FROM Customers:

Question 68

What are the most important SQL Commands?

Answer 68

• SELECT -Extracts data from a database
• UPDATE -Updates data in a database
• DELETE -Deletes data from a database
• INSERT INTO -inserts new data into a database
• CREATE DATABASE -creates a new database
• ALTER DATABASE -modifies a database
• CREATE TABLE -creates a new table
• ALTER TABLE -modifies a table
• DROP TABLE -deletes a table
• CREATE INDEX -creates a index (search key)
• DROP INDEX -Deletes an index

Question 69

What are groups in the Gemfile?

Answer 69

The groups give you the option to perform actions on an entire group.
We also group our gems to make sure that they are used in the right environment.

Question 70

What is rake?

Answer 70

Rake is a gem that allows us to execute commands.

Question 71

Where can I find the Rake commands?

Answer 71

They are in the rakefile

Question 72

What is rake db:create?

Answer 72

It creates an empty database in your application.

Question 73

What is rake db:drop?

Answer 73

It drops your database in your application

Question 74

What is rake db:migrate?

Answer 74

it gives your database a structure. Creating tables and adding columns.

Question 75

How do you generate a new Rails app?

Answer 75

rails new AppName -options

Question 76

How do you start the rails server?

Answer 76

in the terminal

$ rails s

Question 77

How do you create a database?

Answer 77

in the terminal

$ rails db:create

Question 78

What is a scaffold in rails?

Answer 78

A scaffold is the ability to generate multiple items at the same time.

Question 79

How do you create a scaffold in rails?

Answer 79

terminal

$ rails g scaffold FeatureName attribute(like title):datatype(like string)

Question 80

Should you change the schema.rb file?

Answer 80

NEVER

Question 81

What is a before_action in the controller?

Answer 81

The before_action is a method that is run before a controller action.
You use the before action to avoid duplicate code.

Question 82

What is an action in rails?

Answer 82

An action is a ruby method inside a controller

Question 83

What is the difference between the new and create action?

Answer 83

the new action instantiates a new object and sends you to the form.
the create action creates the blogpost

Question 84

What are resources inside the routes.rb?

Answer 84

the resources keyword gives us access to all the associated routes like create, new, edit destroy, index

Question 85

What are initializers in the config folder?

Answer 85

Initializers are files that will be run before the application starts.

ex
you want to connect to an API before the app starts.

Question 86

How do you add files to gitignore?

Answer 86

1) add a comment and add
/folder/file.rb
2) $ git status
3) $ git rm . -r --cached (remove all cache)
4) git status

Question 87

What does a migration do?

Answer 87

The migration changes the schema of the database.

Meaning that the migration changes the database to our new instructions.

Question 88

What is the rails console?

Answer 88

The console is a direct connection to the database

Question 89

What is a seed file?

Answer 89

The seed file allows you to create sample data. You can run ruby code inside it

Question 90

How do you use the seed file?

Answer 90

you run

$ rails db:setup #clears all data and replaces it with the content from the seed file

Question 91

How do you create an index action?

Answer 91

An index action is used when you want to list a number of items and perhaps display them.

1)
class SomeClass < ApplicationController
def index
  @some_items = ModelClass.all
end
end

2)

and create a view (template) under the folder
3)
and add

Question 92

How do you search and find specific routes?

Answer 92

rails routes | grep search_term

Question 93

What is the new action?

Answer 93

The new action displays the form where you enter the information, it is saved and completed in the create action
(only renders the form)

Question 94

What is the create action?

Answer 94

The create action creates and saves the information added through the form in the new action.

Question 95

How do we create the new method?

Answer 95

class SomeClass < ApplicationController
  def new
    @some_item = ModelClass.new
  end
end

And create a view under the right folder and add a form.

Question 96

What does the error message “First argument in form cannot be nil or empty” mean?

Answer 96

It means that the instance variable is missing.

Question 97

How do you create a the create method?

Answer 97

def create
@some_item = ModelClass.new(params[:some_item])
    if @some_item.save
      redirect_to @some_item
    else
      render "new"
    end
  end
end

Question 98

What is routing?

Answer 98

It decides which controller receives which request.

There are often more routes to each controller and they g to different actions

Question 99

What is the purpose of the controller?

Answer 99

It’s purpose is to recive a specific request for the application.

Question 100

What is an action?

Answer 100

An action is a method, its purpose is to collect information to provide to the view.

Question 101

What is a view?

Answer 101

A views purpose is to display information in a human readable way. it gathers its information from an action.

Question 102

How do you create an controller?

Answer 102

$ rails g controller Welcome index

Welcome being the controller name and index being the action (method)

Question 103

What files does a generate controller make?

Answer 103

The command generates:
a controller
a view folder
a view (named as the action)
a route 
a test folder
a test file
a helper folder
a helper file
and stylesheets

Question 104

How do you set a root path?

Answer 104

in config/routes
add
root ‘controller#action’

Question 105

What is a helper method?

Answer 105

A helper method is a method written for the view.

it’s designed to be reusable anywhere on the website, and it cleans up the view code by separating out some logic.

Question 106

What is the null object pattern?

Answer 106

a null object is an object with no referenced value or with defined neutral (“null”) behavior. The null object design pattern describes the uses of such objects and their behavior (or lack thereof).

Question 107

What are view helpers?

Answer 107

they are similar to partials,
They can be called from anywhere in the application
helpers are written in ruby, but partials are written in html

Question 108

How do you check that your new rails app is properly installed?

Answer 108

You run the $ rails about and then run the $ rails s command

Question 109

What are binstubs?

Answer 109

They are wrapper scripts that prepare the environment so that the startup time decreases. It also makes sure that you are running the correct version of ruby.

Question 110

How do you give access to other computers to your rails server?

Answer 110

You need to specify the localhost to 0.0.0.0
by running the command
$ rails server -b 0.0.0.0

Question 111

What does the $ rails g controller command create?

Answer 111

It creates

• a controller file,
• routes to the actions
• a view folder and views files for the actions.

It also creates styling files and test files.

Question 112

How do we add dynamic content to our templates?

Answer 112

We add dynamic content with embedded ruby

Question 113

How do you link to different views in rails?

Answer 113

You use the link_to helper method

Question 114

How can you see all tasks in rails?

Answer 114

with $ rails -T [option]
for example
rails -T db => gives you a list of all db tasks

Question 115

How can you see the migration status?

Answer 115

with the command:

$ rails db:migration:status

Question 116

What is the number_to_currency method?

Answer 116

The number _to_currency method is a view helper that allows you to format a number into a currency

For example:
  Gross: %= number_to_currency(movie.total_gross, 
# options:
precision: 0, # decimals
unit: 'SEK',  # defaults to $
format: '%n %u' # Format of currency 
) 

%>

=> Gross: 200,000,000 SEK

Question 117

How do you clear cache in assets?

Answer 117

rails tmp:clear