跳至主要內容

Rails MVC 架构深入理解

ClownF原创2024/1/21大约 5 分钟RubyRailsMVC架构模式

Rails MVC 架构深入理解

Ruby on Rails 基于 MVC (Model-View-Controller) 架构模式，提供了清晰的代码组织结构和开发约定。

Rails MVC 架构图

Rails MVC 架构
Rails MVC 架构

上图展示了 Rails 的 MVC 架构，让我们深入了解每个组件的作用和交互方式。

Model 层

Model 层使用 Active Record 模式，负责业务逻辑和数据持久化。

基本 Model

# app/models/user.rb
class User < ApplicationRecord
  # 关联关系
  has_many :posts, dependent: :destroy
  has_many :comments
  has_one :profile
  
  # 验证
  validates :email, presence: true, uniqueness: true
  validates :username, presence: true, length: { minimum: 3, maximum: 20 }
  validates :password, length: { minimum: 8 }, if: :password_required?
  
  # 回调
  before_save :normalize_email
  after_create :send_welcome_email
  before_destroy :check_can_delete
  
  # Scope
  scope :active, -> { where(active: true) }
  scope :recent, -> { order(created_at: :desc).limit(10) }
  scope :by_role, ->(role) { where(role: role) }
  
  # 实例方法
  def full_name
    "#{first_name} #{last_name}"
  end
  
  def admin?
    role == 'admin'
  end
  
  # 类方法
  def self.find_by_credentials(email, password)
    user = find_by(email: email)
    user&.authenticate(password) ? user : nil
  end
  
  private
  
  def normalize_email
    self.email = email.downcase.strip
  end
  
  def send_welcome_email
    UserMailer.welcome_email(self).deliver_later
  end
  
  def check_can_delete
    throw(:abort) if admin?
  end
  
  def password_required?
    new_record? || password.present?
  end
end

Model 职责

  • ✅ 定义数据结构和关联
  • ✅ 数据验证
  • ✅ 业务逻辑
  • ✅ 数据库交互
  • ✅ 回调处理
  • ❌ 不处理 HTTP 请求
  • ❌ 不包含视图逻辑

关联关系详解

# app/models/post.rb
class Post < ApplicationRecord
  # 一对多
  belongs_to :user
  has_many :comments, dependent: :destroy
  
  # 多对多 (通过中间表)
  has_many :post_tags
  has_many :tags, through: :post_tags
  
  # 多态关联
  has_many :likes, as: :likeable
  
  # 嵌套属性
  accepts_nested_attributes_for :comments, allow_destroy: true
  
  # 关联查询
  scope :with_user, -> { includes(:user) }
  scope :popular, -> { where('likes_count > ?', 100) }
end

# app/models/comment.rb
class Comment < ApplicationRecord
  belongs_to :post, counter_cache: true
  belongs_to :user
  
  # 自关联 (评论的回复)
  belongs_to :parent, class_name: 'Comment', optional: true
  has_many :replies, class_name: 'Comment', foreign_key: 'parent_id'
end

查询接口

# 基本查询
User.find(1)
User.find_by(email: 'user@example.com')
User.where(active: true)
User.where('created_at > ?', 1.week.ago)

# 链式查询
User.where(role: 'admin')
    .where('created_at > ?', 1.month.ago)
    .order(created_at: :desc)
    .limit(10)

# Scope 查询
User.active.recent.by_role('admin')

# 关联查询 (避免 N+1)
Post.includes(:user, :comments).where(published: true)

# 聚合查询
User.count
User.sum(:posts_count)
User.average(:age)
User.group(:role).count

View 层

View 层负责展示数据，使用 ERB 或 Haml 模板。

ERB 模板

<!-- app/views/users/index.html.erb -->
<div class="users-list">
  <h1>用户列表</h1>
  
  <% if @users.any? %>
    <table class="table">
      <thead>
        <tr>
          <th>用户名</th>
          <th>邮箱</th>
          <th>角色</th>
          <th>操作</th>
        </tr>
      </thead>
      <tbody>
        <% @users.each do |user| %>
          <tr>
            <td><%= link_to user.username, user_path(user) %></td>
            <td><%= user.email %></td>
            <td><%= user.role %></td>
            <td>
              <%= link_to '编辑', edit_user_path(user), class: 'btn btn-sm btn-primary' %>
              <%= link_to '删除', user_path(user), method: :delete, 
                          data: { confirm: '确定删除吗？' }, 
                          class: 'btn btn-sm btn-danger' %>
            </td>
          </tr>
        <% end %>
      </tbody>
    </table>
  <% else %>
    <p>暂无用户</p>
  <% end %>
  
  <%= will_paginate @users %>
</div>

Partial (部分视图)

<!-- app/views/users/_user.html.erb -->
<div class="user-card" id="user-<%= user.id %>">
  <div class="user-avatar">
    <%= image_tag user.avatar_url, alt: user.username %>
  </div>
  <div class="user-info">
    <h3><%= user.username %></h3>
    <p><%= user.email %></p>
    <%= render 'user_stats', user: user %>
  </div>
</div>

<!-- 使用 partial -->
<%= render @users %>
<%= render partial: 'user', collection: @users %>
<%= render 'shared/header' %>

View Helper

# app/helpers/application_helper.rb
module ApplicationHelper
  def formatted_date(date)
    date.strftime('%Y年%m月%d日')
  end
  
  def user_avatar(user, size: 50)
    image_tag user.avatar_url || default_avatar, 
              size: "#{size}x#{size}",
              class: 'rounded-circle'
  end
  
  def flash_class(level)
    {
      'notice' => 'alert-info',
      'success' => 'alert-success',
      'error' => 'alert-danger',
      'alert' => 'alert-warning'
    }[level] || 'alert-info'
  end
end

Controller 层

Controller 层处理 HTTP 请求，协调 Model 和 View。

基本 Controller

# app/controllers/users_controller.rb
class UsersController < ApplicationController
  before_action :authenticate_user!
  before_action :set_user, only: [:show, :edit, :update, :destroy]
  before_action :authorize_user, only: [:edit, :update, :destroy]
  
  # GET /users
  def index
    @users = User.includes(:profile)
                 .page(params[:page])
                 .per(20)
    
    respond_to do |format|
      format.html
      format.json { render json: @users }
    end
  end
  
  # GET /users/:id
  def show
    @posts = @user.posts.published.recent
    
    respond_to do |format|
      format.html
      format.json { render json: @user, include: :posts }
    end
  end
  
  # GET /users/new
  def new
    @user = User.new
  end
  
  # POST /users
  def create
    @user = User.new(user_params)
    
    if @user.save
      flash[:success] = '用户创建成功'
      redirect_to @user
    else
      flash.now[:error] = '创建失败'
      render :new, status: :unprocessable_entity
    end
  end
  
  # GET /users/:id/edit
  def edit
  end
  
  # PATCH/PUT /users/:id
  def update
    if @user.update(user_params)
      flash[:success] = '更新成功'
      redirect_to @user
    else
      flash.now[:error] = '更新失败'
      render :edit, status: :unprocessable_entity
    end
  end
  
  # DELETE /users/:id
  def destroy
    @user.destroy
    flash[:success] = '用户已删除'
    redirect_to users_path
  end
  
  private
  
  def set_user
    @user = User.find(params[:id])
  rescue ActiveRecord::RecordNotFound
    flash[:error] = '用户不存在'
    redirect_to users_path
  end
  
  def user_params
    params.require(:user).permit(
      :username, :email, :password, :password_confirmation,
      :first_name, :last_name, :bio
    )
  end
  
  def authorize_user
    unless current_user == @user || current_user.admin?
      flash[:error] = '权限不足'
      redirect_to root_path
    end
  end
end

Controller 职责

  • ✅ 处理 HTTP 请求
  • ✅ 参数处理
  • ✅ 调用 Model
  • ✅ 准备视图数据
  • ✅ 返回响应
  • ❌ 不包含业务逻辑
  • ❌ 不直接操作数据库

RESTful 路由

# config/routes.rb
Rails.application.routes.draw do
  root 'home#index'
  
  # RESTful 资源路由
  resources :users do
    resources :posts, only: [:index, :show]
    member do
      get 'profile'
      post 'follow'
      delete 'unfollow'
    end
    collection do
      get 'search'
    end
  end
  
  # 嵌套资源
  resources :posts do
    resources :comments, except: [:index]
  end
  
  # 命名空间
  namespace :admin do
    resources :users
    resources :posts
  end
  
  # API 路由
  namespace :api do
    namespace :v1 do
      resources :users, defaults: { format: :json }
    end
  end
end

请求流程

1. 浏览器发送请求
   ↓
2. Router 匹配路由
   ↓
3. Controller 接收请求
   ↓
4. Controller 调用 Model
   ↓
5. Model 查询数据库
   ↓
6. Model 返回数据
   ↓
7. Controller 准备视图数据
   ↓
8. View 渲染模板
   ↓
9. 返回 HTML 响应

最佳实践

1. Skinny Controller, Fat Model

# 不好的做法 - 逻辑在 Controller
class PostsController < ApplicationController
  def publish
    @post = Post.find(params[:id])
    @post.published = true
    @post.published_at = Time.current
    @post.save
    # 发送通知...
    # 更新统计...
  end
end

# 好的做法 - 逻辑在 Model
class PostsController < ApplicationController
  def publish
    @post = Post.find(params[:id])
    @post.publish!
  end
end

class Post < ApplicationRecord
  def publish!
    transaction do
      update!(published: true, published_at: Time.current)
      notify_subscribers
      update_statistics
    end
  end
end

2. Service Objects

# app/services/user_registration_service.rb
class UserRegistrationService
  def initialize(params)
    @params = params
  end
  
  def call
    ActiveRecord::Base.transaction do
      user = create_user
      create_profile(user)
      send_verification_email(user)
      user
    end
  end
  
  private
  
  def create_user
    User.create!(@params.slice(:email, :password))
  end
  
  def create_profile(user)
    user.create_profile!(@params.slice(:first_name, :last_name))
  end
  
  def send_verification_email(user)
    UserMailer.verification_email(user).deliver_later
  end
end

性能优化

N+1 查询问题

# 不好 - N+1 查询
@posts = Post.all
@posts.each do |post|
  puts post.user.name  # 每次都查询数据库
end

# 好 - 预加载
@posts = Post.includes(:user)
@posts.each do |post|
  puts post.user.name  # 使用预加载的数据
end

# 复杂预加载
Post.includes(user: :profile, comments: :user)

缓存

# Fragment 缓存
<% cache @post do %>
  <%= render @post %>
<% end %>

# Russian Doll 缓存
<% cache ['posts', @posts.maximum(:updated_at)] do %>
  <% @posts.each do |post| %>
    <% cache post do %>
      <%= render post %>
    <% end %>
  <% end %>
<% end %>

# Low-level 缓存
def expensive_operation
  Rails.cache.fetch('expensive_operation', expires_in: 12.hours) do
    # 耗时操作
  end
end

总结

Rails 的 MVC 架构通过清晰的职责分离，让代码更易维护和测试。遵循 "约定优于配置" 的原则，能够快速开发出高质量的 Web 应用。

参考资料

最近更新:
贡献者: 1262133427@qq.com