Question

在这里，我首先搜索机票，然后训练预订哪张票。我是承诺的新手，所以我想知道这是正确的方法，还是可以在没有嵌套的情况下完成？

router.get('/ticket/:id', isLoggedIn, (req, res) => {
    Ticket.findById(req.params.id)
    .populate('passengers')
    .exec()
    .then(foundTicket => {
        Train.findById(foundTicket.trainDetails._id)
        .exec()
        .then(foundTrain => {
            res.render("ticket",{ticket:foundTicket, train:foundTrain});
        })
        .catch(err => {
            console.log(err)
        })
    })
    .catch(err => {
        console.log(err)
    })
});

Answer 1

通过回归第二个承诺，哟可以进一步压扁它。 Catch将捕获链中的任何错误。

router.get('/ticket/:id', isLoggedIn, (req, res) => {
    Ticket.findById(req.params.id)
    .populate('passengers')
    .exec()
    .then(foundTicket => {
        return Train.findById(foundTicket.trainDetails._id)
        .exec();
    }).then(foundTrain => {
            res.render("ticket",{ticket:foundTicket, train:foundTrain});
    }).catch(err => {
        console.log(err)
    });
});

Answer 2

是的，您应该flatten it by returning the inner promise以便链接到它并且只需要一个错误处理程序。

router.get('/ticket/:id', isLoggedIn, (req, res) => {
    Ticket.findById(req.params.id).populate('passengers').exec()
    .then(foundTicket =>
        Train.findById(foundTicket.trainDetails._id).exec()
    ).then(foundTrain => {
        res.render("ticket",{ticket:foundTicket, train:foundTrain});
    }, err => {
        console.log(err);
        res.status(500); // don't forget to respond!
    });
});

这是使用承诺的正确方法

2 个答案: