如何在保留数据的同时链接 Promises？

Question

我有两个 API-调用链接如下：

let weatherPromise;

if (crds) {
    weatherPromise = mapbox.getLocation(crds)
    .then(locData => darksky.getWeather(crds))
    .then(weatherData => Object.assign(weatherData, {city: locData.city}));
} else if (term) {
    weatherPromise = mapbox.getCoords(term)
    .then(locData => darksky.getWeather(locData.crds));
} else {
    weatherPromise = Promise.reject({error: 'Aborted due to unexpected POST-Body'});
}

weatherPromise.then(weatherData => {
    io.emit('update', weatherData);
    console.log(`Answer sent: ${JSON.stringify(weatherData)}`);
}, reject => {
    io.emit('update', reject);
    console.error(reject.error);
});

但它根本不起作用。错误处理无处不在（主要是记录 undefined 和失败），例如 locData 在那一秒似乎无法访问 then() 了。我尝试嵌套 Promises 并且效果很好，但我想尽可能避免这种反模式。

Answer 1

你可以，但在这种情况下，我显然会选择异步/等待：

async function retrieveWeather() {
   if (crds) {
      const locData = await mapbox.getLocation(crds);
      const weatherData = await darksky.getWeather(crds);

      return Object.assign(weatherData, {city: locData.city});
   } else if (term) {
     const locData = await mapbox.getCoords(term);
     const weatherData = await darksky.getWeather(locData.crds);

     return weatherData;
   } else {
     throw {error: 'Aborted due to unexpected POST-Body'};
   }
}

(async function sendWeather() {
  try {
    const weatherData = await retrieveWeather();
    io.emit('update', weatherData);
    console.log(`Answer sent: ${JSON.stringify(weatherData)}`);
  } catch(error) {
     io.emit('update', error);
     console.error(reject.error);
  }
})();

如何在保留数据的同时链接 Promises？

How to chain Promises while keeping the data?

javascript

node.js

promise

es6-promise