Question

无论如何只为只读文档设置created_at时间戳吗？

我目前有以下消息类

import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';
import fetch from 'node-fetch';
import PropTypes from 'prop-types';
import { Map, TileLayer } from 'react-leaflet';

export default class PageBackground extends Component{

    constructor(props) {
        super(props);
        this.getLocation=this.getLocation.bind(this);
        this.state={
            position:[2,2]
        };
        }


    componentWillMount() {
        this.getLocation();
    }
    getLocation () {

        fetch('http://freegeoip.net/json/')
         .then((res)=>res.json())
         .then((objec)=>{this.setState({position:[objec.latitude,objec.longitude]});console.log(this.state.position)})
         .catch((err)=>{console.log("didn't connect to App",err);this.setState({position:['10','8']});})
    }

    render(){
        return (
      <Map center={this.state.position} zoom={13} >
        <TileLayer
          attribution='&copy; <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
          url='http://{s}.tile.osm.org/{z}/{x}/{y}.png'/>

        </Map>
        );
        }
    }

它工作正常，但对于每条消息，我都在使用updated_at字段浪费空间，而该字段将始终与created_at相同

Answer 1

浏览this page的时间戳部分。

include Mongoid::Timestamps             - created_at and updated_at.
include Mongoid::Timestamps::Created    - created_at only.
include Mongoid::Timestamps::Updated    - updated_at only.

你甚至可以有短名称

include Mongoid::Timestamps::Short           - c_at and u_at.
include Mongoid::Timestamps::Created::Short  - c_at only.
include Mongoid::Timestamps::Updated::Short  - u_at only.

Answer 2

包括Mongoid::Timestamps::Created而不是Mongoid::Timestamps。

class Message
  include Mongoid::Document
  include Mongoid::Timestamps::Created

  field :text,      type: String

  belongs_to :user, foreign_key: :user_id
  embedded_in :conversation
end

Mongoid仅使用created_at时间戳

2 个答案: