[RUBY] How to store Rakuten API data in a table


If you are developing a web application in a portfolio etc., you may want to use an external API.

With regard to the Rakuten API introduced this time, acquiring data itself is not so difficult. If you get the app ID and install the gem, you can get the data relatively easily.

However, if you try to utilize the acquired data in the app, such as "Store API data in a table and associate it with other tables ...", the difficulty will increase a little (I personally think, lol).

In this article, we will describe "How to store the acquired data in the table" and "Association settings". Also, at the end, I provided a search function in the app and briefly described the code to display the necessary data.

I hope it will be helpful for those who want to use Rakuten API from now on.


――This article refers to Rakuten API. There are various Rakuten APIs, but this time we will use the Rakuten Books Book Search API.

--In this article, we will omit the part of API data acquisition (application ID acquisition and gem installation). For the data acquisition part, please refer to the following article.   https://freesworder.net/rakuten-api-rails/ https://qiita.com/hakusai_it/items/6453c4577647cb8995d3


ER diagram

This time, we will proceed with the discussion with the following ER diagram. The Book table is the table that stores the data. We have set up a Review table to write reviews about the books we have acquired.


Let's take a look at the columns in the Book table. This time, the primary_key of the Book table will use "isbn", which is a unique number of the product, instead of "id". "Title" and "author" are the title and author name of the book, respectively. "Item_caption" is the product description, "item_url" is the url of Rakuten's product, and "middleimage_url" is the image of the book. There are various other data, so if you are interested, please refer to the following URL. https://webservice.rakuten.co.jp/api/booksbooksearch/

Mounting process


We will implement it in the following flow.

step1. Creating a table step2. Association settings step3. Routing settings step4. Controller settings step5. Creating a search page

"Association settings" are step1 and step2, "Store the acquired data in a table" is step3, step4, "Implementation of search page" will be implemented in step5

step1. Creating a table

We will create each table. As mentioned above, this time we will create User, Book, Review tables.

User table creation

The User table hasn't changed. Let's create a model and perform the migration!


$ rails g model User name:string email:string password_digest:string
$ rails g db:migrate

Book table creation

First, we will create a model.


$ rails g model Book title:string author:string isbn:bigint url:string image_url:string

Next, we will rewrite the migration file. Since the primary_key of the Book table uses "isbn", which is the unique number of the product, instead of "id", it is necessary to rewrite the file.

The US mark of the file name is the Migration ID (the number on which the date etc. is written). I think the ActiveRecord :: Migration [6.0] part varies from person to person.

Add null: false, primary_key: true to the isbn part.


class CreateBooks < ActiveRecord::Migration[6.0]
  def change
    create_table :books, id: false do |t|
      t.string :title
      t.string :author
      t.bigint :isbn, null: false, primary_key: true
      t.string :url
      t.string :image_url


After rewriting the migration file, it will be migrated.


$ rails g db:migrate

Review table creation

Finally, we will create a Review table.


$ rails g model Review content:string user:references book:references

Next, we will rewrite the migration file. The US mark of the file name is the Migration ID (the number on which the date etc. is written). I think the ActiveRecord :: Migration [6.0] part varies from person to person.


class CreateReviews < ActiveRecord::Migration[6.0]
  def change
    create_table :books, id: false do |t|
      #foreign mentioned in the book part_key:Delete true
      t.references :book, null: false
      t.references :user, null: false, foreign_key: true

    #The following code is newly added in this part
    add_foreign_key :bookcases, :books, column: :book_id , primary_key: :isbn

After rewriting the migration file, we will execute the migration.


$ rails g db:migrate

This completes the table creation. Next is the association settings.

step2. Association settings

Set the association of each model.rb. Again, write the code so that the primary_key of the Book table is "isbn".


class User < ApplicationRecord
  has_many :reviews, dependent: :destroy


class Book < ApplicationRecord
  self.primary_key = "isbn"
  has_many :reviews, dependent: :destroy


class Bookcase < ApplicationRecord
  belongs_to :user
  belongs_to :book, primary_key: "isbn"

Up to step2, table creation and association settings are complete. Since step3 and after, we will mainly explain how to store data in the Book table, so we will omit the User and Review models and describe only the Book model.

step3. Routing settings

This time, we have provided a search field and a/search action to display the search results. If necessary, set additional actions yourself.


get 'books/search', to: "books#search"

step4. Controller settings

First, create a controller file.


$ rails g controller books

Write the following code in the created controller file.


class BooksController < ApplicationController

  def search
    #Make an empty array here
    @books = []
    @title = params[:title]
    if @title.present?
      #In this part, the data (json data) obtained from Rakuten API is stored in results.
      #This time, we search the title of the book and set it to store the matching data.
      results = RakutenWebService::Books::Book.search({
        title: @title,
      #In this part "@We will store the JSON data obtained from the API in "books".
      #read(result)Is set as a private method.
      results.each do |result|
        book = Book.new(read(result))
        @books << book
    #「@Each data in "books" will be saved.
    #Books that have already been saved have an unless syntax to exclude them.
    @books.each do |book|
      unless Book.all.include?(book)

  #We will set the method of "narrowing down the necessary data from the data of Rakuten API" and "storing the data in the corresponding column".
  def read(result)
    title = result["title"]
    author = result["author"]
    url = result["itemUrl"]
    isbn = result["isbn"]
    image_url = result["mediumImageUrl"].gsub('?_ex=120x120', '')
    book_genre_id = result["booksGenreId"]
    item_caption = result["itemCaption"]
      title: title,
      author: author,
      url: url,
      isbn: isbn,
      image_url: image_url,
      book_genre_id: book_genre_id,
      item_caption: item_caption

By step4, data storage in the table is complete. In step5, we will create a search page and a result output page.

step5. Creating a search page

Create a file called search.html.erb and write the code.


#Show search bar
<%= form_tag(books_search_path, method: :get) do %>
  <%= text_field_tag :title, @title %>
  <%= button_tag type: "submit" %>
<% end %>

#Display search results
<% if @books %>
  <% @books.each do |book| %>
  #Please enter the data you want to display.
  #The code below displays the image, title, author name, and product description.
    <%= image_tag book.image_url %>
    <%= book.title %>
    <%= book.author %>
    <%= book.item_caption %>    
  <% end %>
<% end %>

This is the end of the mounting process. If you have any questions or mistakes, please let us know in the comments.

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