Promise.all 返回 [null， null] 并且不按预期返回

Question

我已经编写了一个promise.all函数，如下所示，它没有返回我预期的结果。

if (Array.isArray(data)) {
    return Promise.all(data.map((data) => {
        hook.app.service('location')
        .find({ query: { serviceLocationId:"100" } })
        .then((result) => {
            var startDept = result.data[0];
            if (result.data.length > 0) {
                data.problem.solutions.solution.routes.route.forEach((d) => {
                    d.stops.unshift({
                        serviceType: '',
                        orders: [],
                        travelTime:'',
                        travelDistance:'',
                        travelCost:'',
                        serviceTime: '',
                        serviceTimeCost:0,
                        tripNumber:0,
                        stopName : startDept.description,
                        arrivalTime:'',
                        departureTime : 36000.0,
                        locationType : startDept.locationType,
                        sequence : 0,
                        locationId : startDept.serviceLocationId,
                        lng : startDept.location.lng,
                        lat : startDept.location.lat
                    });
                    var endDept = d.stops.pop();
                    d.stops.push({
                        serviceType: '',
                        orders: [],
                        travelTime:endDept.travelTime,
                        travelDistance:endDept.travelDistance,
                        travelCost:endDept.travelCost,
                        serviceTime: '',
                        serviceTimeCost:0,
                        tripNumber:0,
                        stopName : startDept.description,
                        arrivalTime : endDept.arrivalTime,
                        departureTime:'',
                        locationType : startDept.locationType,
                        sequence : endDept.sequence,
                        locationId : endDept.locationId,
                        lng : startDept.location.lng,
                        lat : startDept.location.lat
                    });
                });
                hook.data = data;
                combineArr = [];
                return routes(hook).then((hook) => {
                    if ([hook.data].length > 0) {
                        combineArr.push(hook.data);
                        return combineArr;
                    } else {
                        next(new Error('routes response create failed'));
                    }
                }).catch((err) => { return next(new Error(err.error)); });
            } else {
                next(new Error('no depo found'));
            }
        }).catch(err=>{ return next(new Error(err.error)); });
    })).then((results) => {
        console.log(results);
        hook.result = results;
        next();
    });
}

上述承诺返回[null, null] .我没有得到预期的结果。请帮助我解决这个问题。

Answer 1

你没有从map回调返回任何内容，所以生成的数组是一个undefined数组，而不是 promise。您需要返回在回调中得到的承诺，因此数组是承诺数组。

基本上，您正在这样做：

return Promise.all(myArray.map(entry => {
    getAPromise(entry);
}));

。你应该在哪里做

return Promise.all(myArray.map(entry => {
    return getAPromise(entry);
}));

....或

return Promise.all(myArray.map(entry => getAPromise(entry)));