NodeJS我的带有链承诺的SQL查询 [英] NodeJS My SQL query with Chain promise
问题描述
我有3个函数，我想逐步调用此函数，例如，当我将调用firs函数并获取结果时，我必须调用第二个函数并传递从第一次调用返回的参数.完成第二个调用后，我必须调用第三个函数并传递第二个函数返回的参数.
I have 3 function and i want to call this function to step by step, for example when i will call firs function and get result, i have to call second function and pass parameter returned from first call. after i will finish second call i have to call third function and pass parameter returned from second function.
#1:
getCategory = function (branch_id) {
var deferred = q.defer();
var categoryData;
var query = 'SELECT id,name,price,currency FROM category where branch_id=?';
pool.getConnection(function (err, connection) {
connection.query(query, [branch_id], function (error, row, fields) {
if (error) {
deferred.reject(error);
} else {
connection.release();
deferred.resolve(row);
}
});
});
return deferred.promise; }
#2:
getRoom = function (branch_id, categoryID) {
var deferred = q.defer();
var roomData;
var roomSql = 'SELECT id,room_no,name,price,currency FROM room where branch_id=? and category_id=?';
pool.getConnection(function (err, connection) {
connection.query(roomSql, [branch_id, categoryID], function (error, row, fields) {
if (err) {
deferred.reject(err);
} else {
connection.release();
deferred.resolve(row);
}
});
});
return deferred.promise;
}
#3:
getReservationL = function (room_id, start_date, end_date) {
var deferred = q.defer();
var reservationData;
var reservationSql = 'SELECT d.id,d.create_date,d.update_date,d.room_id,d.status_id,d.start_date,d.end_date, ' +
' s.name as status_name,a.id as reservation_id,a.person_no as person_no, p.first_name,p.last_name,p.email ' +
' FROM reservation_detail d ' +
' inner join reservation_status s on d.status_id=s.id ' +
' inner join reservation a on d.reservation_id=a.id ' +
' inner join person p on a.person_no=p.personal_no ' +
' where d.room_id=? and d.start_date >? and d.start_date<?';
pool.getConnection(function (err, connection) {
connection.query(reservationSql, [room_id, start_date, end_date], function (error, row, fields) {
if (err) {
deferred.reject(err);
} else {
connection.release();
deferred.resolve(row);
}
});
});
return deferred.promise;
}
我需要这样的东西:
data = getCategory()
for(i=0;i<data.length;i++){
data[i].room = getRoom(data[i].id);
for(j=0;j<data[i].room[j].length;j++){
data[i].room[j].reservation = getReservationL(data[i].room[j].id);
}
}
如何使用promise或callback在NodeJS中实现此伪代码.我更愿意使用诺言.
How to implement this pseudo code in NodeJS using promise or callback. I would prefer to use promise.
UPDATE#1 在第二次迭代后我得到了这样的数据
UPDATE#1 I have data like this after second iteration
[
{
"id": 64,
"name": "VIP",
"price": 116.5,
"currency": "USD",
"room": [
{
"id": 44,
"room_no": "101",
"name": "A",
"price": 100,
"currency": "EUR"
},
{
"id": 274,
"room_no": "505",
"name": "a",
"price": 1,
"c\r\nurrency": "GEL"
}
]
},
{
"id": 74,
"name": "SUPER VIP",
"price": 110,
"currency": "EUR",
"room": [
{
"id": 54,
"room_no": "102",
"name": "A",
"price": 100,
"currency": "GEL"
},
{
"id": 284,
"room_no": "606",
"name": "a",
"price": 1,
"currency": "GEL"
}
]
},
{
"id": 84,
"name": "DOUBLE",
"price": 110,
"currency": "GEL",
"room": [
{
"id": 204,
"room_no": "103",
"name": "b",
"price": 120,
"currency": "GEL"
}
]
}
]
我想遍历每个类别的每个房间.
I wand to iterate over each category's each room's.
getCategory(branch_id).then(firstRecords => {
let promises = firstRecords.map(function (record) {
return getRoom(branch_id, record.id)
.then(roomData => {
var res = Object.assign({}, record, { room: roomData });
return res;
})
});
return Promise.all(promises);
//HERE i have data that is placed above.
}).then(secondRecords => {
let promises = secondRecords.map(function (category) {
return category.room;
}).map(function (rooms) {
console.log('SECOND', rooms);
return rooms;
}).map(function (reservation) {
console.log('THERD', reservation);
return reservation;
})
return Promise.all(promises);
}).then(reservation => {
console.log("Reservation", reservation);
})
UPDATE#2 最终解决方案在这里
getCategory(branch_id) .then( categories => {
let roomPromises = categories.map( category => {
return getRoom(branch_id, category.id)
.then( rooms => Object.assign({}, category, { rooms }) ) });
return Promise.all(roomPromises) }) .then( category_rooms => {
let finalPromise = category_rooms.map( category => {
let reservationPromises = category.rooms.map( room => {
return getReservationL(room.id, start_date, end_date)
.then( reservations => Object.assign({}, room, { reservations }) )
})
return Promise.all(reservationPromises)
.then( room_reservations => {
return Object.assign({}, category, { rooms: room_reservations })
}); })
// const flattenPromise = finalPromise.reduce( (a, b) => a.concat(b), []); // return Promise.all(flattenPromise);
return Promise.all(finalPromise) }) .then( data => console.log('final: ', data) )
推荐答案
您可以使用 .then 来解决承诺，并且可以链接 then 来同步解决多个承诺时尚.
You can resolve a promise using .then and can chain then to resolve multiple promises in a synchronous fashion.
也许这可以解决您的用例.
Maybe this will solve your use case.
getCategory()
.then( firstRecords => {
console.log('firstRecords: ', firstRecords);
let promises = firstRecords.map( record => getRoom(record) );
return Promise.all(promises);
})
.then( secondRecords => {
console.log('secondRecords: ', secondRecords);
let promises = secondRecords.map( record => getReservationL(record) );
return Promise.all(promises);
})
.then( thirdRecords => {
console.log('thirdRecords: ', thirdRecords);
})
参考: then方法返回一个Promise，它允许方法链接.
The then method returns a Promise which allows for method chaining. 如果该函数作为处理程序传递给，然后返回一个Promise，则等效的Promise将暴露给方法链中的后续对象 If the function passed as handler to then returns a Promise, an equivalent Promise will be exposed to the subsequent then in the method chain 引用:承诺全部 Promise.all()方法返回一个Promise，当可迭代参数中的所有promise已解决或可迭代参数不包含promise时，该Promise进行解析.它拒绝的原因是第一个承诺被拒绝. The Promise.all() method returns a single Promise that resolves when all of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with the reason of the first promise that rejects.
您可以执行类似的操作来实现您在评论中提到的内容. you could do something like this to achieve the what you have mentioned in comments. 如果要附加第一个和第二个诺言的数据，则在那儿解析诺言只能在一个地方访问两个诺言的数据. If you want to append the data of the first and second promise, then resolve the promises there only to access the data of both in one place. 正如您在评论中提到的那样，此代码可能会对您有所帮助. As you mentioned in comments, this code might help you. 这篇关于NodeJS我的带有链承诺的SQL查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
Promise.all([ { key: 1 }, Promise.resolve(3), 1, true ])
.then( results => {
results[0]; // { key: 1 }
results[1]; // 3
results[2]; // 1
results[3]; // true
})
更新#1
Promise.all 仅接受一个promise数组，而不接受键上带有promise的对象.Update #1
Promise.all only accept an array of promise and not object with promises on the key.# wrong
Promise.all([
{ key: Promise.resolve(1) },
{ key: Promise.resolve(2) },
{ key: Promise.resolve(3) },
])
# right
Promise.all([
Promise.resolve(1),
Promise.resolve(2),
Promise.resolve(3)
])
getCategory(branch_id)
.then( firstRecords => {
console.log('firstRecords: ', firstRecords);
let promises = firstRecords.map( record => {
return getRoom(branch_id, record.id)
.then( roomData => Object.assign({}, record, { room : roomData }) )
});
return Promise.all(promises)
})
getCategory(branch_id)
.then( categories => {
let roomPromises = categories.map( category => {
return getRoom(branch_id, category.id)
.then( rooms => Object.assign({}, category, { rooms }) )
});
return Promise.all(roomPromises)
})
.then( category_rooms => {
let finalPromise = category_rooms.map( category => {
let reservationPromises = category.rooms.map( room => {
return getReservationL(room.id, start_date, end_date)
.then( reservations => Object.assign({}, room, { reservations }) )
})
return Promise.all(reservationPromises)
.then( room_reservations => {
return Object.assign({}, category, { rooms: room_reservations })
});
})
return Promise.all(finalPromise)
})
.then( data => console.log(data) )
