我如何 return 从承诺到我的调用函数的值？

Question

我的理解是，我正在调用一个同步函数 "httpGet"，它应该返回一个承诺。该函数似乎可以正常工作，因为它通过 console.log 语句成功地从 Airtable 获取了我的所有数据，但我在 .then() 方法中得到了任何响应。

这里是我调用 "httpGet" 函数的地方：

async handle(handlerInput) {
    let speechText = '';
    console.log('Going to fetch Airtable data');
    await httpGet(base).then((response) => {
      console.log('have promise')    
    }).catch((err) => {
      //set an optional error message here
      console.log('do not have promise')
      //speechText = 'there is an error ' + err.message;
    }); 
    speechText = `Container ID ` + contID + ` is a ` + bincolor + `, ` + gallons + ` located in ` + binloc ;        

    console.log('speechText = ' + speechText);

    return handlerInput.responseBuilder
      .speak(speechText)
      .reprompt(speechText)
      .withSimpleCard('Warehouse Inventory', speechText)
      .getResponse();
};

这是正在调用的 httpGet 函数：

async function httpGet(options) {
  // return new pending promise
  return new Promise((resolve, reject) => {    

        base('Bins').select({
          // Selecting a record in Grid view:
          maxRecords: 1,
          view: "Grid view"
        }).eachPage(function page(records, fetchNextPage) {
          // This function (`page`) will get called for each page of records.

          records.forEach(function(record) {
              console.log('Container ID: ', record.get('Container ID'));
              console.log('Gallons: ', record.get('Gallons'));        
              console.log('Bin Color: ', record.get('Color'));
              console.log('Location: ', record.get('Location'));        
              console.log('Imperfections: ', record.get('Imperfections'));
              var contID = record.get('Container ID');
              var gallons = record.get('Gallons');
              var bincolor = record.get('Color');
              var binloc = record.get('Location');
              var imper = record.get('Imperfections');

          });

          // To fetch the next page of records, call `fetchNextPage`.
          // If there are more records, `page` will get called again.
          // If there are no more records, `done` will get called.
          fetchNextPage();

      }, function done(err) {
          if (err) { 
            console.error(err); return; 
          }
      });    
  });
}

最终，我试图获取存储在变量 contID、加仑、bincolor、binloc 和 imper 中的值。我该如何做到这一点？

Answer 1

在 httpGet() 中，执行 resolve({ contID, gallons, /* ... */ })，然后在 then((response) => {}) 中，您的 response 将成为具有 contID、gallons 的对象，等属性。查看 this blog post 了解有关异步 return 值的更多详细信息。

Answer 2

您的代码有太多嵌套，这是一种不好的做法。你不能 return 从承诺中获取价值，因为它是异步的，你可以在其中做你想做的事。

    httpGet = (options) => {
    return new Promise((resolve, reject) => {
        resolve(/*return your result here*/);
        reject(/*return error here*/);
    });
}


//inside of some function
let firstResult, secondResult;
httpGet(argument)
    .then(result => {
        firstResult = result;
        //you can chain promise if u need
        return httpGet(secondArgument)
    })
    .then(result => {
        secondResult = result;
    })
    .then(() => {
        //here you can acces firstResult, secondResult variables, pass them to some function as arguments
    })
    .catch((error)=>{})

我如何 return 从承诺到我的调用函数的值？

How do I return a value from a promise to my calling function?

javascript

alexa