nodejs中的Promise不能处理错误，不能处理函数

Question

我在node.js中做了一个承诺，并尝试在控制器中使用它。但它抛出了一个错误，即'not a function'。并且调用没有小括号的promises抛出了一个错误'Can't call then on undefined'。

Promise代码：

const Subscription = require("../models/subscription");

exports.pickRandomSubscription = new Promise(function(resolve, reject) {
    let pickedSubscription = '';
    Subscription.find({}, function(err, subscriptions) {
        subscriptions.forEach(function(item) {
            pickedSubscription = item;  //get last subscription
        });
        if (pickedSubscription) resolve(pickedSubscription);
        else reject("Subscription not found");
    });
})

应许的召唤：

const { pickedRandomSubscription } = require("../algo/pickSubscription");
let pickedSubscription = '';
pickedRandomSubscription().then(res => pickedSubscription = res).catch(console.log)

Answer 1

您将直接导出promise，而不是函数。你可能想这样做：

exports.pickRandomSubscription = () => new Promise(function(resolve,reject) { ... }

Answer 2

导入了错误的promise名称：pickedRandomSubscription

const { pickedRandomSubscription } = require("../algo/pickSubscription");

您应该将其修复为：pickRandomSubscription (而不是ed)

const { pickRandomSubscription } = require("../algo/pickSubscription");