订阅、取消订阅、订阅列表

订阅表设计

订阅表存储， 订阅与被订阅的关系

module.exports = app => {
  const mongoose = app.mongoose
  const Schema = mongoose.Schema
  const subscriptionSchema = new Schema({
    user: { // 订阅用户
      type: mongoose.ObjectId,
      ref: 'User',
      required: true
    },
    channel: { // 订阅频道
      type: mongoose.ObjectId,
      ref: 'User',
      required: true
    },
    createdAt: { // 创建时间
      type: Date,
      default: Date.now
    },
    updatedAt: { // 更新时间
      type: Date,
      default: Date.now
    }
  })
  return mongoose.model('Subscription', subscriptionSchema)
}

订阅

• 将订阅者id、被订阅者id 存储在订阅关系表中
• 被订阅者的数量完成加1

• 订阅者的数量完成加1

  await new Subscription({
    user: userId, // 订阅者id
    channel: channelId // 被订阅者id
  }).save()

  取消订阅

• 删除订阅关系表中的数据

• 被订阅者数量完成减1
• 订阅者数量完成减1

  const record = await Subscription.findOne({
    user: userId,
    channel: channelId
  })
  await record.remove() // 删除关系表中的订阅关系

  获取订阅列表

  let subscriptions = await Subscription.find({
    user: this.ctx.params.userId // 被订阅者 id
  }).populate('channel')

  获取订阅列表 并查出订阅列表里的视频信息（关联表查询）

  const res = await Subscription.aggregate([
      {
        $match:{ user: mongoose.Types.ObjectId('63217ccac4a5416000d2bd99')}
      },
      {
        $lookup:
          {
            from: "users",
            localField: "channel",
            foreignField: "_id",
            as: "user_info"
          }
      },
      {
        $lookup:
          {
            from: "videos",
            localField: "channel",
            foreignField: "user",
            as: "videos_info"
          }
      },
      {
        $lookup:
          {
            from: "subscriptions",
            localField: "channel",
            foreignField: "user",
            as: "subscriptons_info"
          }
      },
    ])