尝试解析来自 ES6 class 函数的承诺链

Question

所以我有这个 class 称为事件，我正在尝试从我的服务器调用异步函数。我试图了解我哪里出错了/如何解决另一个异步调用中的承诺。任何提示或技巧将不胜感激。

这是我正在调用的事件函数：

Event.prototype.getCost = function(name_of_place){
 return new Promise( function(){
      var placeID;
      var GooglePlaces = require("node-googleplaces");
      const places = new GooglePlaces(API_KEY);
      const params = {
           location: '40.689247,-123.102192',
           radius: 1000
      };
      var query =
      {
            query: name_of_place
       };
       // ASYNC call
       places.textSearch(query).then((res) => {
            console.log("FIRST ASYNC CALL");
            console.log(res.body.results[0].place_id);
            placeID = res.body.results[0].place_id;
            var request_place_details={
                 placeid : placeID
            };
            console.log(request_place_details);

            return request_place_details;

       }).then((request_place_details) => {
            console.log("SECOND ASYNC CALL");
            places.details(request_place_details).then((res) => {
                 console.log(res.body.result.price_level + "   S");
                 var cost = res.body.result.price_level;
                 //trying to resolve getCost promise
                 //resolve(this.cost);
                 return cost;
            }).then((cost) => {
                 console.log("ATTEMPT TO RESOLVE ORIGINAL");
                 this.cost = cost;
                 console.log(cost + "   F");

                 //WANT TO RETURN THIS VALUE IN THE END
                 resolve(this.cost);
            });
       });
  })};

这是我调用它的地方：

//Server is currently serving on port 8420
app.listen(8420,function startServer(){
 console.log("Listening on :: " + 8420);
 var Event1 = new events(7,10,'New York');
 // console.log(Event1.getCost('Sushi'));
 Event1.getCost('Sushi').then(res => {
      console.log(res);
 })
});

Answer 1

你没有正确声明承诺，return new Promise( function(resolve, reject){}

然后你就可以像这样使用了

places.details(request_place_details).then((res) => {
             console.log(res.body.result.price_level + "   S");
             var cost = res.body.result.price_level;


             // Just resolve it here.
             resolve(cost);                 
        });


// And here, res == cost.
Event1.getCost('Thai Moon').then(res=> {
  console.log(res);
})

另请参阅 Promise docs。

Answer 2

你的整个结构太复杂了。剥离注释时，您可以将代码简化为：

Event.prototype.getCost = function(name_of_place){
    var GooglePlaces = require("node-googleplaces");
    const places = new GooglePlaces(API_KEY);
    //const params = {
    //  location: '40.689247,-123.102192',
    //  radius: 1000
    //};

    return places.textSearch({ query: name_of_place })
        .then(res => res.body.results[0].place_id)
        .then(placeID => places.details({ placeid : placeID }))
        .then(res => res.body.result.price_level)
}

尝试解析来自 ES6 class 函数的承诺链

Trying to resolve a promise chain from ES6 class functions

javascript

node.js

es6-promise