在Rails中存储联接模型数据 [英] Store Join Model Data in Rails

问题描述

我是Ruby on Rails的新手，并且正在开发后端API.

I'm new to Ruby on Rails, and I'm developing a backend API.

目前，我有两种Active Record模型，分别是 Book 和 Genre .

Currently, I got 2 Active Record Models called Book and Genre.

class Book < ActiveRecord::Base
    has_and_belongs_to_many :genres
end

class Genre < ActiveRecord::Base
    hast_and_belongs_to_many :books
end

数据库架构模型

create_table :books do |t|
  t.string "title"
end

create_table :genres do |t|
  t.string "genre"
end

create_join_table :books, :genres do |t|
  t.index [:book_id, :genre_id]
  t.index [:genre_id, :book_id]
end

REST POST请求

 # POST /book
    def create
        book= Book.new(books_params)

        if book.save
            render json: {status: 'SUCCESS', message:'Book Saved', data: book},status: :ok
        else
            render json: {status: 'ERROR', message: 'Booknot saved', data: book.errors}, status: :unprocessable_entity
        end 

    end

private
    def books_params
        params.require(:book).permit(:title)
    end

问题

我想发出HTTP发布请求，以使用类型创建一本新书.我已经测试过书的插入(没有类型，只传递书名)，它可以完美地工作.不过，我也想添加一些流派类别.

QUESTION

I'd like to make an HTTP Post request to create a new book with it's genres. I've already tested the book insertion (without genres, just passing the book name), it works perfectly. However I'd also like to add some genre categories.

推荐答案

两者 has_many和has_and_belongs_to_many类方法创建一组_ids setter和getter:

Both the has_many and has_and_belongs_to_many class methods create a set of _ids setters and getters:

book = Book.new
book.genre_ids = [1, 2, 3]
book.genre_ids == [1, 2, 3] # true

这些设置器将自动创建和删除联接表中的行.由于 ActiveModel :: AttributeAssignment 将哈希参数映射到.new，和.create设置模型中的设置器，只需将genre_ids参数列入白名单:

These setters will automatically create and delete rows in the join table. Since ActiveModel::AttributeAssignment maps the hash argument to .new, .update and .create to setters in the model all you need to do is whitelist the genre_ids parameter:

def books_params
  params.require(:book).permit(:title, genre_ids: [])
end

传递空数组将允许允许的标量值的数组例如数字或字符串.

Passing an empty array permits an array of permitted scalar values like for example numericals or strings.

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