Rails Toy App

Changing the homepage from 'Hello' to '/users'

Inside config > routes.rb:

Rails.application.routes.draw do
  resources :users

  root 'application#hello'
end

The line resources :users is created when we scaffolded the User table.

From here we can change the root 'application#hello' to:

Rails.application.routes.draw do
  resources :users

  root 'users#index'
end

The prefix determines the controller we are reading from. The suffix is the function that returns some data needed to render the page. What this code then does is calls on app > models > user.rb to grab all the users defined from the controller @users = User.all. It then gets used in app > views > users > index.html.erb to iterate through all the Users and display them on the page.

How does the /edit route know which user to edit?

At the top of the user controller, there is a before_action :set_user, only: %i[ show edit update destroy ] line that runs only before the specified action, edit included. This way a user is set before the edit action and then the action goes through and lead into app > views > users > edit.html.erb which renders the page.

Weakness of scaffold

No data validations.
No authentication (logging in/out).
No styling

Microposts

When first scaffolding the Microposts, the text collumn will allow for more than 140 characters. To circumvent this, we can limit it with the length validator. Length Validator Inside app > models > micropost.rb we can add the validation to limit the amount of characters the post can be.

class Micropost < ApplicationRecord
    validates :content, lengthL { maximum: 140 }
end

Associations

To create associations between tables, go into their respective model files. Input the code belongs_to :table or has_many :tables to create the association.

How to navigate through the table associations

first_user = User.first grabs the first user and assigns it to the variable first_user.
first_user.microposts returns all the microposts with the user_id equal to the id of first_user.
micropost.user returns the user associated with the post.

Table associations through migrations

YouTube

The video covers creating separate tables, using migrations to create associations and deleting unecessary columns from tables.

One way we can also create associations through migrations is to run the command

$ bin/rails g migration add_user_to_microposts user:references

This creates a a new migration file with the code

class AddUserToMicroposts < ActiveRecord::Migration
  def change
    add_reference :micropost, :user, null:false, foreign_key:true
  end
end

Null constraint and foreign key attributes are assigned by default. Once the migration is ran via

$ bin/rails db:migrate

The schema file should update the microposts table with

t.integer "user_id"

Once that is done, you can now add the has_many or belongs_to in the respective model files. To test this, we can populate the tables via

$ rails c
> user = User.create!(attributes:value)
> micropost = Micropost.create!(attributes:value, user: user)

When we populate the microposts, we assign the user attribute to the user variable we created before it. If it works, we are able to run these commands and have it return the appropriate values.

> user.microposts
> micropost.user

When deploying to Heroku, it won't know the tables/relations we have created. To run the migrations we have created:

$ heroku run rails db:migrate

What We Learned in this Chapter

Scaffolding automatically creates code to model data and interact with it through the web.
Scaffolding is good for getting started quickly but is bad for understanding.
Rails uses the model-view-controller (MVC) pattern for structuring web applications.
As interpreted by Rails, the REST architecture includes a standard set of URLs and controller actions for interacting with data models.
Rails supports data validations to place constraints on the values of data model attributes.
Rails comes with built-in functions for defining associations between different data models.
We can interact with Rails applications at the command line using the Rails console.

nguyntyler/rails-toy-app