如何在 firebase 中调用 yield read API

Question

我有一个 redux saga API，我正在连接到 firebase 并读取数据记录。

var roomRef = firebase.database().ref('/Users/' + userid + '/rooms')
  var rooms = []
  roomRef.once('value', function (snap) {
    var roomkeys = snap.val()
    for (var roomkey in roomkeys) {
      firebase.database().ref('/Rooms/' + roomkey).once('value', function (item) {
        rooms.push(item.val())
      })
    }
    console.log(rooms)
   --> put({type: 'LOAD_ROOMS', payload: { rooms: rooms}})
  })

因为我的 put 在回调函数中，所以我不能使用 yield 关键字。如何分派事件以使用新值 'rooms'

更改 reducer 的状态

Answer 1

解决此问题的方法是将回调转换为承诺。 redux-saga 知道如何解决您传递给 call effect 的承诺。但是 call 需要一个函数，而不是一个 promise。来自文档：

If the result is a Promise, the middleware will suspend the Generator until the Promise is resolved, in which case the Generator is resumed with the resolved value. or until the Promise is rejected, in which case an error is thrown inside the Generator.

var roomRef = firebase.database().ref('/Users/' + userid + '/rooms')
var rooms = yield call(function() {
  return new Promise(function(resolve, reject) {
    roomRef.once('value', function (snap) {
      var rooms = []
      var roomkeys = snap.val()
      for (var roomkey in roomkeys) {
        firebase.database().ref('/Rooms/' + roomkey).once('value', function (item) {
          rooms.push(item.val())
        })
      }
      resolve(rooms)
    })
  })
})
yield put({type: 'LOAD_ROOMS', payload: { rooms: rooms}})

如何在 firebase 中调用 yield read API

How to call yield in firebase read API

firebase

firebase-realtime-database

redux

redux-saga