用has_scope实现Rails API筛选

做接口的时候，遇到了筛选的问题，不知如何去处理，Google了下，发现了个很简单的解法，实测有效，附上。

问题描述

现有model product，category, schema中信息如下：

Table name products

id          :integer
title       :string
description :string
price       :float
category_id :integer

Table name  categories
id          :integer
title       :string

app/models/product.rb中：

class Product < ActiveRecord::Base
  belongs_to :category
  ......
end

app/models/category.rb中：

class Category < ActiveRecord::Base
  has_many :products
  ......
end

app/controllers/api/v1/products_controller.rb中：

class Api::V1::ExperiencesController < Api::V1::BaseController
# GET /api/v1/products
  def index
    @products = Product.all
    render json: @products
  end
end

现在需要得到指定category的products，类似这样：/api/v1/products?category=1，得到category是1的所有products。以及给定价格区间的products，类似这样：/api/v1/products?price[from]=100&price[to]=999

如何实现？

试试has_scope

解答

三步走

• 安装has_scope gem

  gemfile中添加：

  gem 'has_scope'
  

  终端bundle，服务器重启。

• 在model中添加scope

  修改app/models/product.rb：

  class Product < ActiveRecord::Base
    belongs_to :category
  
   + scope :category, -> (category_id) { where(category_id: category_id) }
   + scope :price, -> (from, to) { where("price >= ? AND price <= ?", from, to) }
    ......
  
  end
  

• 在controller中添加has_scope

  修改app/controllers/api/v1/products_controller.rb：

  class Api::V1::ExperiencesController < Api::V1::BaseController
    + has_scope :category, only: :index
    + has_scope :price, using: [:from, :to], only: :index
  
  # GET /api/v1/products
    def index
    -  @products = Product.all
    +  @products = apply_scopes(Product).includes(:category).all
        # using includes(:category), fix N+1 query problem
      render json: @products
    end
  end
  

  好，大功告成，用postman测试下，确认正常，cool！

参考

Rails API Filtering and Sorting

has_scope