Javascript Promise内部Promise在bluebird节点中创建不可管理的结构
我的查询如下:Javascript Promise内部Promise在bluebird节点中创建不可管理的结构,javascript,node.js,Javascript,Node.js,我的查询如下: checkUserId(user_email).then((info) => { changeBookStatus(bookInfo._id, borrow).then(() => { issueReturnBook(info._id, bookInfo._id, due_date + "/" + due_month, bor
checkUserId(user_email).then((info) => {
changeBookStatus(bookInfo._id, borrow).then(() => {
issueReturnBook(info._id, bookInfo._id,
due_date + "/" + due_month, borrow).then((savedInfo) => {
console.log("saved info " + savedInfo._id);
LibraryTransaction.findById(savedInfo._id).
populate('UserDetails').populate('BookDetails').exec((err, libInfo) => {
res.json({
status: '200',
message: 'transaction completed',
data: libInfo
});
});
}).catch((err) => {
res.json({
status: '500',
message: err
});
});
}).catch((err) => {
res.json({
status: '500',
message: err
});
});
})
const issueReturnBook = (user_id, book_id, due_date, borrow) => {
let borrowReturn;
if (borrow == '0') {
borrowReturn = false;
} else if (borrow == '1') {
borrowReturn = true;
}
return new Promise((resolve, reject) => {
const libraryTransaction = new LibraryTransaction();
libraryTransaction.UserDetails = user_id;
libraryTransaction.BookDetails = book_id;
libraryTransaction.DueDate = due_date;
libraryTransaction.BorrowReturn = borrowReturn;
libraryTransaction.save().then((info) => {
if (!info) {
reject(false);
}
resolve(info);
}).catch((err) => {
reject(err);
});
});
};
const changeBookStatus = (book_id, borrow) => {
let borrowStat;
if (borrow == '0') {
borrowStat = false;
} else if (borrow == '1') {
borrowStat = true;
}
return new Promise((resolve, reject) => {
Books.findOneAndUpdate({ '_id': book_id }, { $set: { CurrentlyAvailableStatus: borrow } }).then((info) => {
if (!info) {
reject('there is no such book');
}
resolve(info);
}).catch((err) => {
reject(err);
});
});
};
const checkUserId = (user_email) => {
return new Promise((resolve, reject) => {
User.findOne({ 'Email': user_email.trim() }).then((info) => {
if (!info) {
reject('the is no such user');
}
resolve(info);
}).catch((err) => {
reject(err);
});
});
};
现在,里面有太多了,那么,有没有更好的方法来有效地执行它呢?很难判断哪些变量在范围内,哪些库事务函数返回承诺。但我想你想要这样的东西:
checkUserId(user_email)
.then(info => {
return changeBookStatus(bookInfo._id, borrow)
// This is here so we can return "info" to the next function. You might want to
// wrap this "changeBookStatus(...).then(...)" part in its own function.
.then(() => {
return info;
});
})
.then(info => {
return issueReturnBook(info._id, bookInfo._id, due_date + "/" + due_month, borrow);
})
.then(savedInfo => {
console.log("saved info " + savedInfo._id);
LibraryTransaction
.findById(savedInfo._id)
.populate('UserDetails')
.populate('BookDetails').exec((err, libInfo) => {
res.json({
status: '200',
message: 'transaction completed',
data: libInfo
});
});
})
.catch(err => {
res.json({
status: '500',
message: err
});
});
请注意,我包含了返回语句,以明确每个承诺都需要返回,以便正确链接。但是你可以移除它们来清理东西:
checkUserId(user_email)
// The extra ".then" is still here for the reasons mentioned above
.then(info => changeBookStatus(bookInfo._id, borrow).then(() => info))
.then(info => issueReturnBook(info._id, bookInfo._id, due_date + "/" + due_month, borrow))
.then(savedInfo => {
console.log("saved info " + savedInfo._id);
LibraryTransaction
.findById(savedInfo._id).
populate('UserDetails')
.populate('BookDetails').exec((err, libInfo) => {
res.json({
status: '200',
message: 'transaction completed',
data: libInfo
});
});
})
.catch(err => {
res.json({
status: '500',
message: err
});
});
书中几乎所有的都有。我应该这样写吗thensavedInfo=>return savedInfo而不是thensavedInfo=>{}这样做没有意义。thensavedInfo=>savedInfo-这与没有then是一样的。我想你还需要一个关于Library事务的承诺…填充…执行-目前它忽略了错误。最好也为此编写一个额外的Promission函数。