<%= debug(params) if Rails.env.development? %>

@import "bootstrap-sprockets";
@import "bootstrap";

/* mixins, variables, etc. */

$gray-medium-light: #eaeaea;

@mixin box_sizing {
  -moz-box-sizing:    border-box;
  -webkit-box-sizing: border-box;
  box-sizing:         border-box;
}
.
.
.
/* miscellaneous */

.debug_dump {
  clear: both;
  float: left;
  width: 100%;
  margin-top: 45px;
  @include box_sizing;
}

resources :users

User.find(params[:id])

<% provide(:title, @user.name) %>
<h1>
  <%= gravatar_for @user %>
  <%= @user.name %>
</h1>

module UsersHelper

  # 引数で与えられたユーザーのGravatar画像を返す
  def gravatar_for(user)
    gravatar_id = Digest::MD5::hexdigest(user.email.downcase)
    gravatar_url = "https://secure.gravatar.com/avatar/#{gravatar_id}"
    image_tag(gravatar_url, alt: user.name, class: "gravatar")
  end
end

<% provide(:title, @user.name) %>
<div class="row">
  <aside class="col-md-4">
    <section class="user_info">
      <h1>
        <%= gravatar_for @user %>
        <%= @user.name %>
      </h1>
    </section>
  </aside>
</div>

class UsersController < ApplicationController

  def show
    @user = User.find(params[:id])
  end

  def new
    @user = User.new
  end
end

<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>

<div class="row">
  <div class="col-md-6 col-md-offset-3">
    <%= form_for(@user) do |f| %>
      <%= f.label :name %>
      <%= f.text_field :name %>

      <%= f.label :email %>
      <%= f.email_field :email %>

      <%= f.label :password %>
      <%= f.password_field :password %>

      <%= f.label :password_confirmation, "Confirmation" %>
      <%= f.password_field :password_confirmation %>

      <%= f.submit "Create my account", class: "btn btn-primary" %>
    <% end %>
  </div>
</div>

<%= form_for(@user) do |f| %>
  .
  .
  .
<% end %>

def create
    @user = User.new(params[:user])    # 実装は終わっていないことに注意!
    if @user.save
      # 保存の成功をここで扱う。
    else
      render 'new'
    end
  end

@user = User.new(params[:user])

class UsersController < ApplicationController
  .
  .
  .
  def create
    @user = User.new(user_params)
    if @user.save
      # 保存の成功をここで扱う。
    else
      render 'new'
    end
  end

  private

    def user_params
      params.require(:user).permit(:name, :email, :password,
                                   :password_confirmation)
    end
end

<% provide(:title, 'Sign up') %>
<h1>Sign up</h1>

<div class="row">
  <div class="col-md-6 col-md-offset-3">
    <%= form_for(@user) do |f| %>
      <%= render 'shared/error_messages' %>

      <%= f.label :name %>
      <%= f.text_field :name, class: 'form-control' %>

      <%= f.label :email %>
      <%= f.email_field :email, class: 'form-control' %>

      <%= f.label :password %>
      <%= f.password_field :password, class: 'form-control' %>

      <%= f.label :password_confirmation, "Confirmation" %>
      <%= f.password_field :password_confirmation, class: 'form-control' %>

      <%= f.submit "Create my account", class: "btn btn-primary" %>
    <% end %>
  </div>
</div>

$mkdir app/views/shared

<% if @user.errors.any? %>
  <div id="error_explanation">
    <div class="alert alert-danger">
      The form contains <%= pluralize(@user.errors.count, "error") %>.
    </div>
    <ul>
    <% @user.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
    </ul>
  </div>
<% end %>

require 'test_helper'

class UsersSignupTest < ActionDispatch::IntegrationTest

  test "invalid signup information" do
    get signup_path
    assert_no_difference 'User.count' do
      post users_path, params: { user: { name:  "",
                                         email: "user@invalid",
                                         password:              "foo",
                                         password_confirmation: "bar" } }
    end
    assert_template 'users/new'
  end
end

before_count = User.count
post users_path, ...
after_count  = User.count
assert_equal before_count, after_count

def create
    @user = User.new(user_params)
    if @user.save
      redirect_to @user
    else
      render 'new'
    end
  end

redirect_to user_url(@user)

def create
    @user = User.new(user_params)
    if @user.save
      flash[:success] = "Welcome to the Sample App!"
      redirect_to @user
    else
      render 'new'
    end
  end

<!DOCTYPE html>
<html>
  .
  .
  .
  <body>
    <%= render 'layouts/header' %>
    <div class="container">
      <% flash.each do |message_type, message| %>
        <div class="alert alert-<%= message_type %>"><%= message %></div>
      <% end %>
      <%= yield %>
      <%= render 'layouts/footer' %>
      <%= debug(params) if Rails.env.development? %>
    </div>
    .
    .
    .
  </body>
</html>

$ rails db:migrate:reset

test "valid signup information" do
    get signup_path
    assert_difference 'User.count', 1 do
      post users_path, params: { user: { name:  "Example User",
                                         email: "user@example.com",
                                         password:              "password",
                                         password_confirmation: "password" } }
    end
    follow_redirect!
    assert_template 'users/show'
  end

config.force_ssl = true