Gem hash_map_attributes 将 JSON 类型的字段映射为具体的方法，方便 CRUD
项目地址：
https://github.com/SuMingXuan/hash_map_attributes/
写这个插件是因为目前在我做写业务的时候，需要预留一个 json 字段方便以后数据的扩展，并且方便 CRUD。比如我有一个 pages 表包含了一个 jsonb 类型的字段（extra_data），extra_data 里面可能存很多额外的属性或者是目前我们没有考虑到的属性。让我痛苦的是，对这种类型的字段操作 CRUD 会让代码变得非常难看。
Usage
class Page < ApplicationRecord
# == Schema Information
#
# Table name: special_channels
#
# id :bigint not null, primary key
# description :string
# title :string
# extra_data :jsonb
# created_at :datetime not null
# updated_at :datetime not null
include HashMapAttributes
hash_map_attributes :image_url, to: :extra_data
hash_map_attributes :background_url, prefix: :content, to: :extra_data
end
page = Page.new(image_url: 'http://www.image.com/example1.png', content_background_url: 'http://www.image.com/example2.png')
page.save
page.image_url #=> http://www.image.com/example1.png
page.content_background_url #=> http://www.image.com/example2.png
page.update(image_url: ' http://www.image.com/example3.png')
page.image_url #=> http://www.image.com/example3.png
查询
如果是 jsonb 的话，那么则支持查询
Page.where_hash(image_url: 'http://www.baidu.com', content_background_url: 'http://www.baklib.com')
控制台会打印如下查询语句
SELECT "pages".* FROM "pages" WHERE (pages.extra_data->>'image_url' = 'http://www.baidu.com' and pages.extra_data->>'background_url' = 'http://www.baklib.com')
补充：现在支持嵌套 json 的查询和修改了，但是取消了指定前缀的参数。
是这样的，笔误了
这个是 ActiveRecord::Store 可以完成的事情呀
https://api.rubyonrails.org/v5.2.0/classes/ActiveRecord/Store.html
class User < ActiveRecord::Base
store :settings, accessors: [ :color, :homepage ], coder: JSON
store :parent, accessors: [ :name ], coder: JSON, prefix: true
store :spouse, accessors: [ :name ], coder: JSON, prefix: :partner
store :settings, accessors: [ :two_factor_auth ], suffix: true
store :settings, accessors: [ :login_retry ], suffix: :config
end
u = User.new(color: 'black', homepage: '37signals.com', parent_name: 'Mary', partner_name: 'Lily')
u.color # Accessor stored attribute
u.parent_name # Accessor stored attribute with prefix
u.partner_name # Accessor stored attribute with custom prefix
u.two_factor_auth_settings # Accessor stored attribute with suffix
u.login_retry_config # Accessor stored attribute with custom suffix
u.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor
# There is no difference between strings and symbols for accessing custom attributes
u.settings[:country] # => 'Denmark'
u.settings['country'] # => 'Denmark'
# Dirty tracking
u.color = 'green'
u.color_changed? # => true
u.color_was # => 'black'
u.color_change # => ['black', 'red']
