---
# System prepended metadata

title: Active Storage
tags: [寫一半]

---

---
tags: 寫一半
---

:::warning
Active Storage 整理中
:::


Active Storage
===

### 1. 新建立專案, database 使用 postgresql (若已建立可省略這步驟)
>專案名稱以 MinimalistNote 為例

```console
範例:  $ rails new [projectName] [--database=postgresql]
```

```=
$ rails new MinimalistNote --database=postgresql
```
#### 若專案已存在，但需要將資料庫轉移到 postgresql
>TODO


### 2. 進入專案目錄中, 安裝 Active Storage
>to create migration to add active storages two table to application.

```console
$ cd MinimalistNote

$ rails active_storage:install

```

### 3. 執行 migration
`rails active_storage:install` 會在 `db/migrate` 中產生一個migration. 

>![](https://i.imgur.com/8QqJPxH.png)

:::spoiler **migration 檔案內容** (點擊查看)

```ruby=
# This migration comes from active_storage (originally 20170806125915)
class CreateActiveStorageTables < ActiveRecord::Migration[5.2]
  def change
    create_table :active_storage_blobs do |t|
      t.string   :key,          null: false
      t.string   :filename,     null: false
      t.string   :content_type
      t.text     :metadata
      t.string   :service_name, null: false
      t.bigint   :byte_size,    null: false
      t.string   :checksum,     null: false
      t.datetime :created_at,   null: false

      t.index [ :key ], unique: true
    end

    create_table :active_storage_attachments do |t|
      t.string     :name,     null: false
      t.references :record,   null: false, polymorphic: true, index: false
      t.references :blob,     null: false

      t.datetime :created_at, null: false

      t.index [ :record_type, :record_id, :name, :blob_id ], name: "index_active_storage_attachments_uniqueness", unique: true
      t.foreign_key :active_storage_blobs, column: :blob_id
    end

    create_table :active_storage_variant_records do |t|
      t.belongs_to :blob, null: false, index: false
      t.string :variation_digest, null: false

      t.index %i[ blob_id variation_digest ], name: "index_active_storage_variant_records_uniqueness", unique: true
      t.foreign_key :active_storage_blobs, column: :blob_id
    end
  end
end


```
:::


執行 migration, 將 Active Storage 產生的資料表(tables) 寫進資料庫中，欄位結構可以從 `db/schema` 檔案中查看


```console
$ rails db:migrate # to migrate tese new tables into schema file.
```

:::spoiler **db/schema 檔案內容** (點擊查看)

```ruby
# This file is auto-generated from the current state of the database. Instead
# of editing this file, please use the migrations feature of Active Record to
# incrementally modify your database, and then regenerate this schema definition.
#
# This file is the source Rails uses to define your schema when running `bin/rails
# db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
# be faster and is potentially less error prone than running all of your
# migrations from scratch. Old migrations may fail to apply correctly if those
# migrations use external dependencies or application code.
#
# It's strongly recommended that you check this file into your version control system.

ActiveRecord::Schema.define(version: 2021_09_01_005659) do

  # These are extensions that must be enabled in order to support this database
  enable_extension "plpgsql"

  create_table "active_storage_attachments", force: :cascade do |t|
    t.string "name", null: false
    t.string "record_type", null: false
    t.bigint "record_id", null: false
    t.bigint "blob_id", null: false
    t.datetime "created_at", null: false
    t.index ["blob_id"], name: "index_active_storage_attachments_on_blob_id"
    t.index ["record_type", "record_id", "name", "blob_id"], name: "index_active_storage_attachments_uniqueness", unique: true
  end

  create_table "active_storage_blobs", force: :cascade do |t|
    t.string "key", null: false
    t.string "filename", null: false
    t.string "content_type"
    t.text "metadata"
    t.string "service_name", null: false
    t.bigint "byte_size", null: false
    t.string "checksum", null: false
    t.datetime "created_at", null: false
    t.index ["key"], name: "index_active_storage_blobs_on_key", unique: true
  end

  create_table "active_storage_variant_records", force: :cascade do |t|
    t.bigint "blob_id", null: false
    t.string "variation_digest", null: false
    t.index ["blob_id", "variation_digest"], name: "index_active_storage_variant_records_uniqueness", unique: true
  end

  add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
  add_foreign_key "active_storage_variant_records", "active_storage_blobs", column: "blob_id"
end

```
:::










---

### 參考資料
