NodeJS Promise 和异步问题 (Firebase)

Question

问题出在 promise 和异步函数上。 "All moved" 应该在 async.each 中的所有内容完成后记录。但是什么都没有记录。

这是我的导出函数：

var courier_id = data.ref.parent.key;
return admin.database().ref("firewall_queue/"+courier_id+"/orders").once('value',function(orders){
    //console.log(Object.keys(orders.val()));
    async.each(Object.keys(orders.val()), function (order, callback) {
        if(order != "none") {
            return moveToWaitingFromFirewall(order).then(callback())

        }
    },
    function (err) {
        console.log("All moved");
        return admin.database().ref("/firewall_queue/"+courier_id+"/orders/").remove().then(()=>{
            return pushToPending(courier_id,data.ref.key);
        })
    });
})

这是我的 moveToWaitingFromFirewall 函数：

function moveToWaitingFromFirewall(order_id){
var order = {};
order.id = order_id;
var promises = [];
promises.push(new Promise((resolve) => {
    admin.database().ref("orders/"+order_id+"/zone").once('value').then(function(zone){
        order.zone = zone.val();
        resolve();
    })

}))
promises.push(new Promise((resolve) => {
    admin.database().ref("orders/"+order_id+"/time_order_placed").once('value').then(function(time_order_placed){
        order.time = time_order_placed.val();
        resolve();
    })
}))
//grab zone and time first
return Promise.all(promises).then(()=>{
    return admin.database().ref(order.zone+"/wait_order_queue/"+order.id).set(order.time);
})

}

JSON Firebase

"c98" : {
    "orders" : {
      "0333" : 123123,
      "0345" : 12,
      "0911" : 123,
      "none" : "none"
    }

Answer 1

稍微研究一下，也许可以应用到您当前的代码中。

想象一下 admin.database().ref("orders/"+order_id+"/time_order_placed").once('value') 就像 delay(time)

// let delay = time => new Promise(res=>setTimeout(res,time));
let delay = function(time){
  return new Promise(function(resolve,reject){
    setTimeout(function(){ 
      resolve();
    },time);
  });
}

let myPromise = function(order){
  return Promise.all([
    delay(500),
    delay(500),
    delay(1000).then(function(){
      console.log('Order complete: ',order);
      return; // returns undefined, so cb doesn't pass anything to cb(err), but use ()=>cb() to avoid this anyways.
    })
  ]);
}

let orders = [1,2,3];

async.each(orders,function(order,cb){
  myPromise(order)
  .then(()=>cb())
  .catch(err=>cb(err));
},function(err,data){
  if(err){
    console.log('Err',err);
  }else{
    console.log('all Finished');
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/async/2.6.0/async.js"></script>

NodeJS Promise 和异步问题 (Firebase)

NodeJS Promise and Async Problems (Firebase)

node.js

firebase

firebase-realtime-database

firebase-admin