哈囉，大家好！

到目前為止Model 關聯性終於建好了、資料庫也很粗淺地加上了關聯，但seeding tasks 遲遲還沒處理好，總覺得資料多樣性還是不夠。

前幾天多虧公司前輩指引了JSONPlaceholder 這網站，其主要用途為提供：

Free fake API for testing and prototyping.

但資料有關聯且多樣性非常夠，很適合用來當seeding data，爛書心想應該只要自己建立幾個Model 加上關聯，就能搭配這些data 使用了吧？呵......

可因為打API 返回的資料格式是JSON，這篇插話想介紹如何把這些資料跟自己的專案結合囉！

首先我們先來看JSONPlaceholder 的guide，可看到資料的關聯大致是：posts have many comments, albums have many photos......

而fetch Post API 返回的資料則是這形態：

[
  {
    "userId": 1,
    "id": 1,
    "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
    "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
  },
...
]

而這些資料的來源網址為：https://jsonplaceholder.typicode.com/posts

因此我打算先建立一個Post Model 及其table，並嘗試用JSONPlaceholder 來seeding 我的Post data：

前置步驟：

# 1. new 專案、以PG 為database
❯ rails new rookie_sql_sample_db --database=postgresql

# 2. 建立資料庫
❯ rails db:create

# 3. create Model & table of Post
❯ rails g model Post userId:integer title:string body:string

# 4. 建立一個seedings task
❯ rails g task seeding_posts seed_posts

好了之後讓我們進去console 試試看吧！

require 'open-uri'
# 先require'open-uri' 的標準函式庫

open('https://jsonplaceholder.typicode.com/posts')
# 利用open 方法將JSON 來源網址存成一個IO 檔

open('https://jsonplaceholder.typicode.com/posts').read
# 讀取該IO 檔

❯ "[\n  {\n    \"userId\": 1,\n    \"id\": 1,\n    \"title\": \"sunt aut facere repellat provident occaecati excepturi optio reprehenderit\",\n    \"body\": \"quia et suscipit\\nsuscipit recusandae consequuntur expedita et cum\\nreprehenderit molestiae ut ut quas totam\\nnostrum rerum est autem sunt rem eveniet architecto\"\n  },\n  {\n    \"userId\": 1,\n    \"id\": 2,\n    \"title\": \"qui est esse\",\n    \"body\": \"est rerum tempore vitae\\nsequi sint nihil reprehenderit dolor beatae ea dolores neque\\nfugiat blanditiis voluptate porro vel nihil molestiae ut reiciendis\\nqui aperiam non debitis possimus qui neque nisi nulla\"\n  },\n  {\n    \"userId\": 1,\n    \"id\": 3,\n    \"title\": \"ea molestias q

# 應該就能看到資料啦！

接著我們修改剛剛的seeding task:

# 修改task
namespace :seeding_posts do
  desc "TODO"
  task seed_posts: :environment do
    puts "seeding posts"
    Post.destroy_all

    post_data = JSON.parse(open('https://jsonplaceholder.typicode.com/posts').read)
    post_data.each do |post|
      Post.create(userId: post["userId"], title: post["title"], body: post["body"])
    end
    puts "completed"
  end
end

執行task、進console
❯ rails seeding_posts:seed_posts

irb(main):001:0> Post.first
  Post Load (0.3ms)  SELECT "posts".* FROM "posts" ORDER BY "posts"."id" ASC LIMIT $1  [["LIMIT", 1]]
#<Post:0x00007fa36352e5c8> {
            :id => 1,
        :userId => 1,
         :title => "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
          :body => "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto",
    :created_at => Sat, 24 Sep 2022 10:05:04 UTC +00:00,
    :updated_at => Sat, 24 Sep 2022 10:05:04 UTC +00:00
}

就成功帶出資料囉！嘿嘿......

那麼今天的研究就到這邊，謝謝大家~~