More Rails!

Validations, Associations, Params, Heroku, and more!

Today:

  • Models:
    • Validations
    • Associations
  • Controller:
    • Strong parameters
  • Views
    • Partials
  • Heroku

YOU ARE HERE

Model

Validations

Validations

validates :attribute, { validators }

OR

validates_validator_of [ :attributes ]

Associations

  • has_many
    • A Student has many Grades
  • belongs_to
    • Grades belong to Students
  • has_one
    • A Teacher has one Class

Associations

class Student < ActiveRecord::Base
   has_many :grades
end
class Grade < ActiveRecord::Base
   belongs_to :student
end
name age major id
Bob 20 EECS 1
Alice 19 Bio 2
id grade student_id
100 4 1
101 3 1

Primary Key

Foreign Key

name age major id
Bob 20 EECS 1
Alice 19 Bio 2
id grade student_id
100 4 1
101 3 1

Primary Key

Foreign Key

Associations

student = Student.find(1)
student.grades

Controller

Params

  • Dictionary that contains information about the request made. (Controller, action, url, etc.)
def show
    @user = User.find params[:id]
end
  • Also contains form parameters, url parameters, ids, etc.

Params

class PostsController < ApplicationController
  def index
    @post = Post.new
    @posts = Post.all
  end

  def create
    puts params
    @post = Post.new post_params
    @post.save
    redirect_to root_path
  end

  def like
  end

  private

  def post_params
    params.require(:post).permit(:text)
  end
endclass PostsController < ApplicationController
  def index
    @post = Post.new
    @posts = Post.all
  end

  def create
    puts params
    @post = Post.new post_params
    @post.save
    redirect_to root_path
  end

  def like
  end

  private

  def post_params
    params.require(:post).permit(:text)
  end
end

Params

Problem:

User

  • name
  • age
  • major
  • admin

Strong parameters

Problem:

User

  • name
  • age
  • major
  • admin

Strong parameters

BUT

curl -d "user[name]=Charles" 
     -d "user[major]=EECS" 
     -d "user[age]=20" 
     -d "user[admin]=true" 
http://localhost:3000/users

Strong Params

  • Define whitelisted attributes that you can create a model with.
def user_params
    params.require(:user).permit(:name, :age, :major)
end
curl -d "user[name]=Charles" 
     -d "user[major]=EECS" 
     -d "user[age]=20" 
     -d "user[admin]=true" 
http://localhost:3000/users

Strong Params

def create
    @user = User.new params[:user]
end

def create
    @user = User.new user_params
end

private 

def user_params
    params.require(:user).permit(:name, :age, :major)
end

BECOMES

View

Partials

BEFORE

<div class="html-file-1">
    <nav>
        <ul>
	    <li><a href="#">Home</a></li>
            <li><a href="#">About</a></li>
    	    <li><a href="#">Clients</a></li>
	    <li><a href="#">Contact Us</a></li>
        </ul>
    </nav>
</div>
<div class="html-file-2">
    <nav>
        <ul>
	    <li><a href="#">Home</a></li>
            <li><a href="#">About</a></li>
    	    <li><a href="#">Clients</a></li>
	    <li><a href="#">Contact Us</a></li>
        </ul>
    </nav>
</div>
<div class="html-file-4">
    <nav>
        <ul>
	    <li><a href="#">Home</a></li>
            <li><a href="#">About</a></li>
    	    <li><a href="#">Clients</a></li>
	    <li><a href="#">Contact Us</a></li>
        </ul>
    </nav>
</div>
<div class="html-file-3">
    <nav>
        <ul>
	    <li><a href="#">Home</a></li>
            <li><a href="#">About</a></li>
    	    <li><a href="#">Clients</a></li>
	    <li><a href="#">Contact Us</a></li>
        </ul>
    </nav>
</div>

app/views/users/file1.html

app/views/users/file2.html

app/views/users/file3.html

app/views/users/file4.html

Partials

After

<div class="html-file-3">
    <%= render "shared/partial" %>
</div>
<nav>
    <ul>
	<li><a href="#">Home</a></li>
        <li><a href="#">About</a></li>
    	<li><a href="#">Clients</a></li>
        <li><a href="#">Contact Us</a></li>
    </ul>
</nav>
<div class="html-file-1">
    <%= render "shared/partial" %>
</div>
<div class="html-file-2">
    <%= render "shared/partial" %>
</div>
<div class="html-file-4">
    <%= render "shared/partial" %>
</div>

app/views/shared/_partial.html.erb

app/views/users/file1.html.erb

app/views/users/file2.html

app/views/users/file3.html

app/views/users/file4.html

Partials

<%= hello %>
<nav>
    <ul>
	<li><a href="#">Home</a></li>
        <li><a href="#">About</a></li>
    	<li><a href="#">Clients</a></li>
        <li><a href="#">Contact Us</a></li>
    </ul>
</nav>

app/views/shared/partial.html.erb

<div class="html-file-4">
    <%= render "shared/partial", hello: "Hello" %>
</div>

app/views/users/file4.html

Discussion 5 - More Rails

By Charles Xue

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Discussion 5 - More Rails

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