Question

这是我的承诺

findBookings()  
    .then(Promise.all([findInvoiceSum, findReceipt]))
    .then(sendResult)
    .catch(err => {
        console.log("getBookingList ERR: " + err);
        res.json({error:true,err})
    }
)

我会怀疑它运行findBookings（）并且当它解析时它将使用（[findInvoiceSum，findReceipt]）运行链，当两者都完成时，它将运行sendResult。

不幸的是，这是从控制台日志中发生的事情

=====START findInvoiceSum=====
=====START findReceipt=====
=====START findBookings=====
=====RESOLVE findInvoiceSum=====
=====RESOLVE findReceipt=====
=====RESOLVE findBookings=====
=====sendResult=====
=====RESOLVE sendResult=====

为什么？为什么我的第一个承诺被忽略了.then？

这是我的控制器：

// 
// The FIRST promise that needs to be resolved
// 
var findBookings = function() {
    return new Promise((resolve, reject) => {
    console.log("=====START findBookings=====")
    bookingTable.aggregate([
        ...lots of code...
    ], function (err, data) {
        if (!err) {
            bookingArray = data;
            console.log("=====RESOLVE findBookings=====")
            resolve(data);
        } else {
            reject(new Error('findBooking ERROR : ' + err));
        };
    });
})};


// 
// The findInvoiceSum chain promise
// 
var findInvoiceSum = new Promise(
    (resolve, reject) => {
    console.log("=====START findInvoiceSum=====")
    invoiceSumTable.aggregate([
        ...lots of code...
    ], function (err, data) {
        if (!err) {
            console.log("=====RESOLVE findInvoiceSum=====")
            resolve(data);
        } else {
            reject(new Error('findExpense ERROR : ' + err));
        };
    });
});


// 
// The findReceipt chain promise
// 
var findReceipt = new Promise(
    (resolve, reject) => {
    console.log("=====START findReceipt=====")
    receiptTable.aggregate([
        ...lots of code...
    ],function(err, data) {
        if (!err) {
            console.log("=====RESOLVE findReceipt=====")
            resolve(data);
        } else {
            reject(new Error('ERR findPropert : ' + err));
        };
    });
});


// 
// Send the result 
// 
var sendResult = function([invoiceArray, receiptArray]) {
    return new Promise((resolve, reject) => {
        console.log("=====sendResult=====")
        res.json({error:false,  
           "booking":bookingArray, 
           "invoice":invoiceArray, 
           "receipt":receiptArray})
        console.log("=====RESOLVE sendResult=====")
        resolve();
    });
};


// 
// Run the promises
// 
findBookings()  
    .then(Promise.all([findInvoiceSum, findReceipt]))
    .then(sendResult)
    .catch(err => {
        console.log("getBookingList ERR: " + err);
        res.json({error:true,err})
    }
)

Answer 1

我会怀疑它运行findBookings（），当它解决了它然后将使用（[findInvoiceSum，findReceipt]）
运行链

要完成此任务，您需要传递一个函数

findBookings()  
    .then(() => Promise.all([findInvoiceSum(), findReceipt()]))

并使findInvoiceSum和findReceipt成为一个函数。

function findReceipt() {
 return new Promise(
    (resolve, reject) => {
    console.log("=====START findReceipt=====")
    receiptTable.aggregate([
        ...lots of code...
    ],function(err, data) {
        if (!err) {
            console.log("=====RESOLVE findReceipt=====")
            resolve(data);
        } else {
            reject(new Error('ERR findPropert : ' + err));
        };
    });
  });
}

Answer 2

由于您尚未包裹findInvoiceSum和findReceipt 函数承诺是自己初始化的，您可以将promises包装到函数中，并使用Promise.all，如下所示

var findBookings = function() {
    return new Promise((resolve, reject) => {
        console.log("=====START findBookings=====")
        bookingTable.aggregate([
            ...lots of code...
        ], function(err, data) {
            if (!err) {
                bookingArray = data;
                console.log("=====RESOLVE findBookings=====")
                resolve(data);
            } else {
                reject(new Error('findBooking ERROR : ' + err));
            };
        });
    })
};


// 
// The findInvoiceSum chain promise
// 
var findInvoiceSum = function() {
    return new Promise(
        (resolve, reject) => {
            console.log("=====START findInvoiceSum=====")
            invoiceSumTable.aggregate([
                ...lots of code...
            ], function(err, data) {
                if (!err) {
                    console.log("=====RESOLVE findInvoiceSum=====")
                    resolve(data);
                } else {
                    reject(new Error('findExpense ERROR : ' + err));
                };
            });
        });
};


// 
// The findReceipt chain promise
// 
var findReceipt = function() {
    return new Promise(
        (resolve, reject) => {
            console.log("=====START findReceipt=====")
            receiptTable.aggregate([
                ...lots of code...
            ], function(err, data) {
                if (!err) {
                    console.log("=====RESOLVE findReceipt=====")
                    resolve(data);
                } else {
                    reject(new Error('ERR findPropert : ' + err));
                };
            });
        });
};


// 
// Send the result 
// 
var sendResult = function([invoiceArray, receiptArray]) {
    return new Promise((resolve, reject) => {
        console.log("=====sendResult=====")
        res.json({
            error: false,
            "booking": bookingArray,
            "invoice": invoiceArray,
            "receipt": receiptArray
        })
        console.log("=====RESOLVE sendResult=====")
        resolve();
    });
};

// Find invoicesum and receipt
var invoiceAndReceipt = function() {
    return Promise.all([findInvoiceSum(), findReceipt()]).then(function(data) {
        Promise.resolve(data);
    }).catch(function(error) {
        Promise.reject(error);
    });
}

// 
// Run the promises
// 
findBookings()
    .then(invoiceAndReceipt)
    .then(sendResult)
    .catch(err => {
        console.log("getBookingList ERR: " + err);
        res.json({ error: true, err })
    });

为什么承诺会忽略。然后当你在.then中有一个Promise.all时

2 个答案: