ruby-on-rails - Active Record 和文件：如何用我的数据编写 Json 文件？

Question

如何将表事件中的数据写入 json 文件？请看这段代码：

在模型 event.rb

 class Event < ActiveRecord::Base
  attr_accessible :name, :event_description, :start_at, :end_at, :status, :eventable_id
  has_event_calendar
  belongs_to :eventable, polymorphic: true
  after_save :write_json


end
def write_json
    Event.all.each do |event|
            @eventJson = {
            "id" => event.id,
            "start" => event.start_at,
            "end" => event.end_at,
            "title" => event.name,
            "body" => event.event_description,
            "status" => event.status
            } 

    end
    File.open("public/event.json","w") do |f|
      f.write(@eventJson.to_json)
    end 

 end

在文件Json中有一条记录，但在表event中有很多记录。保存记录后如何将表中的所有记录写入eventevent.json 文件？

公共/事件.json

{"id":35,"start":"2013-03-28T00:00:00Z","end":"2013-03-28T00:00:00Z","title":"1345edrewrewr","body":"123124","status":"Confirm"}

Answer 1

问题是您@eventJson在循环中分配了一个值，因此以前的值会丢失。你应该使用一个数组：

def write_json
  events_json = []
  Event.all.each do |event|
    event_json = {
      "id" => event.id,
      "start" => event.start_at,
      "end" => event.end_at,
      "title" => event.name,
      "body" => event.event_description,
      "status" => event.status
    } 
    events_json << event_json
  end
  File.open("public/event.json","w") do |f|
    f.write(events_json.to_json)
  end 
end

Answer 2

在这种情况下，您可能想要使用map而不是each-- 它更清洁。鉴于您说该方法在模型中，这就是它的外观。

class Event < ActiveRecord::Base
    ...

    def self.write_json
      record_json = self.all.map{ |record| { self.name => record.attributes } }.to_json
      File.open("#{Rails.root}/#{(self.name.underscore)}.json", "w") do |f|
        f.write record_json
      end 
    end
end

Answer 3

您可以通过以下方式进行操作：

  def write_json
    File.open('public/event.json', 'w') { |f| f.write(Event.all.to_json) }
  end

如果要保存特定字段，可以这样操作：

  def write_json
    File.open('public/event.json', 'w') do |f|
      f.write(Event.select(:id, :start, :end, :title, :body, :status).to_json)
    end
  end