postgresql Active Record 和文件：如何用我的数据编写 Json 文件？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/15270522/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Active Record and file: How do i write Json file with my data?
提问by King Dark
How do I write a data in table event to json file? Please see this code:
如何将表事件中的数据写入 json 文件？请看这个代码：
In model event.rb
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
In file Jsonthere's one record, but in table eventthere are many records. How do I write all records from table eventto event.json file after saving the record?
在文件中Json有一条记录，但在表中event有许多记录。event保存记录后，如何将表中的所有记录写入event.json 文件？
public/event.json
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"}
回答by Ilya Khokhryakov
The problem is that you assign a value to @eventJsonin a loop so the previous values are lost. You should use an array:
问题是您@eventJson在循环中分配了一个值，因此之前的值会丢失。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
回答by PBJ
In this case, you might want to use mapinstead of each-- it's much cleaner.
Given that you said the method is in the model, this is how it would look.
在这种情况下，您可能想要使用map而不是each- 它更干净。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
