What does that even mean in terms of the following code, the res.send works fine however in my console i get the following message:
http.js:689
throw new Error('Can\'t set headers after they are sent.');
app.get('/summoner/:summonerName', function(req, res) {
lolapi.Summoner.getByName(req.params.summonerName, function(err, obj) {
var options = {
beginIndex: 0,
endIndex: 1
};
lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function(err, matches) {
var gameMatches = matches.matches;
for(var i = 0; i < gameMatches.length; i++) {
lolapi.Match.get(gameMatches[i].matchId, function(err, games) {
res.send({profile : obj, matchHistory : games});
});
}
});
});
});
As I explained in my comments, you are calling res.send() inside a for loop which means you are calling it more than once. You can only call it once per request. That is why you are seeing the error message in the console.
It is not clear exactly what your code really wants to do, but if the desire is to collect all the results into an array and send them all as the response, then you can do that like this:
app.get('/summoner/:summonerName', function (req, res) {
lolapi.Summoner.getByName(req.params.summonerName, function (err, obj) {
if (err) {
return res.status(500).end();
}
var options = {beginIndex: 0, endIndex: 1};
lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function (err, matches) {
var gameMatches = matches.matches;
var results = [];
for (var i = 0; i < gameMatches.length; i++) {
lolapi.Match.get(gameMatches[i].matchId, function (err, games) {
if (err) {
return res.status(500).end();
}
results.push({profile: obj, matchHistory: games});
// if all results are done, then send response
if (results.length === gameMatches.length) {
res.json(results);
}
});
}
});
});
});
Note: I've also added rudimentary error handling.
If you want the results in the particular order that you requested then, then you can add a little more code to do that like this:
app.get('/summoner/:summonerName', function (req, res) {
lolapi.Summoner.getByName(req.params.summonerName, function (err, obj) {
if (err) {
return res.status(500).end();
}
var options = {beginIndex: 0, endIndex: 1};
lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function (err, matches) {
var gameMatches = matches.matches;
var results = new Array(gameMatches.length);
var cntr = 0;
for (var i = 0; i < gameMatches.length; i++) {
(function(index) {
lolapi.Match.get(gameMatches[i].matchId, function (err, games) {
if (err) {
return res.status(500).end();
}
++cntr;
results[index] = {profile: obj, matchHistory: games};
// if all results are done, then send response
if (cntr === gameMatches.length) {
res.json(results);
}
});
})(i);
}
});
});
});
Since Promises are now standard in 2016, here's an idea what this could look like using the Bluebird promise library:
const Promise = require('bluebird');
Promise.promisifyAll(lolapi.Summoner);
Promise.promisifyAll(lolapi.MatchList);
Promise.promisifyAll(lolapi.Match);
app.get('/summoner/:summonerName', function (req, res) {
var main;
lolapi.Summoner.getByNameAsync(req.params.summonerName).then(function(obj) {
main = obj;
var options = {beginIndex: 0, endIndex: 1};
return lolapi.MatchList.getBySummonerIdAsync(obj['savisaar2'].id, options);
}).then(function(matches) {
var gameMatches = matches.matches;
return Promise.map(gameMatches, function(item){
return lolapi.Match.getAsync(item.matchId).then(function(games) {
return {profile: main, matchHistory: games};
});
});
}).then(function(results) {
res.json(results);
}).catch(function(err) {
res.status(500).end();
});
}
Related
I'm working on a nodeJS script and I would like to know how to execute a function after an another one.
Because actually i need to save in my database some data and then retrieve them. However for the moment my retrieve is executed before my save :/
Have already looked on internet there is a lot of example I tried them but for the moment no one worked ... I should probably do something wrong if somebody could help me on it :)
function persistMAP(jsonData, callback) {
console.log(jsonData);
//Deck persistance
for (var i = 0; i < 1; i++) {
(function(i) {
var rowData = new DeckDatabase({
_id: new mongoose.Types.ObjectId(),
DeckNumber: Number(jsonData.Deck[i].DeckNumber),
x: Number(jsonData.Deck[i].x),
y: Number(jsonData.Deck[i].y),
});
rowData.save(function(err) {
if (err) return console.log(err);
for (var i = 0; j = jsonData.Units.length, i < j; i++) {
(function(i) {
var unit = new MapDatabase({
//UnitID: mongoose.ObjectId(jsonData.Units[i].UnitID),
UnitID: jsonData.Units[i].UnitID,
TypeID: Number(jsonData.Units[i].TypeID),
x: Number(jsonData.Units[i].x),
y: Number(jsonData.Units[i].y),
_id: mongoose.Types.ObjectId(jsonData.Units[i].Code + 'dd40c86762e0fb12000003'),
MainClass: jsonData.Units[i].MainClass,
Orientation: jsonData.Units[i].Orientation,
Postion: jsonData.Units[i].Postion,
Deck: String(rowData._id)
});
unit.save(function(err) {
if (err) return console.log(err);
console.log('save');
});
})(i);
}
});
})(i);
}
callback();
};
app.get("/Map", function(req, res) {
console.log("got");
var urlTempBox = 'http://localhost:3000/MapCreate';
DeckDatabase.find(null, function(err, data) {
if (err) {
throw (err);
}
if (data.length != 0) {
MapDatabase.find()
.populate('Deck')
.exec(function(err, finalData) {
res.send(finalData);
});
} else {
request(urlTempBox, data, function(error, response, body) {
if (error) {
throw (error);
} else {
var jobj = JSON.parse(response.body);
console.log("persist begin");
persistMAP(jobj, function() {
console.log('retrieve Done');
});
}
});
}
});
You can use javascript callbacks like this:
User.findById(user_id,function(err,data){
//Inside this you can call another function.
});
console.log("Hello"); //this statement won't wait for the above statement
The more good approach would be use promises.
You can also use async await function to handle asynchronus tasks.
Async Await Style
async function getData(){
let user_data=await User.findById(user_id);
let user_videos=await Videos.findById(user_data._id); //user_data._id is coming from the above statement
}
But you can only use await in async methods.
Hope it helps.
i can not figure out why my array is empty while the console is showing output:
I'm fetching data from dynamodb and trying to make a modified response json array i can print the values of dynamodb response but when i push it into array the returned array is empty here is my code.
Here is Util.js file
const dynamo = require('./dynamo.js')
var myjson = [];
exports.myjson = [];
exports.maketimetabledata = function(callback) {
var table = "timetable";
for (i = 1; i <= 2; i++) {
dynamo.docClient.get({
TableName: table,
Key: {
"id": i
}
}, function(err, data) {
if (err) {
console.error("Unable to read item. Error JSON:", JSON.stringify(err, null, 2));
return err;
} else {
dynamores = JSON.parse(JSON.stringify(data));
myjson.push(i);
}
});
console.log(myjson);
}
callback("done");
};
and here is my partial index file:
app.get('/', (req, res) => {
var myjson = [];
util.maketimetabledata(function(returnvalue) {
if (returnvalue) {
console.log(util.myjson);
}
});
});
output :
[] [] []
undefined
{ response from dynamo db for debugging purpose}
Assuming dynamo.docClient.get() returns a Promise, You can use Promise.all() to wait for all the promise to complete then invoke the callback method.
//Use Promise.all()
exports.maketimetabledata = function (callback) {
var table = "timetable";
for (i = 1; i <= 2; i++) {
var table = "timetable";
var promiseArray = [];
for (i = 1; i <= 2; i++) {
var promise = dynamo.docClient.get({
//Your code
});
promiseArray.push(promise)
}
console.log(myjson);
}
Promise.all(promiseArray).then(function () {
callback(myjson);
});
};
//Usage
util.maketimetabledata(function (myjson) {
if (returnvalue) {
console.log(myjson);
}
});
If the method is not returning Promise
var promise = new Promise(function (resolve, reject) {
dynamo.docClient.get({
TableName: table,
Key: {
"id": i
}
}, function (err, data) {
if (err) {
console.error("Unable to read item. Error JSON:", JSON.stringify(err, null, 2));
reject();
return err;
} else {
dynamores = JSON.parse(JSON.stringify(data));
myjson.push(i);
resolve();
}
});
});
var data = [10,21,33,40,50,69];
var i = 0;
var dataSeq = [];
while(i<data.length){
if(data[i]%2 == 0){
store.findOne({'visibility': true},function(err, data){
dataSeq.push(i)
i++;
});
}
else{
dataSeq.push(i)
i++;
}
}
if(i==data.length-1){
console.log(dataSeq) // Should Print [1,2,3,4,5]
return res.status(200).send({ message: 'Task Completed'})
}
I want to collect data as per loop excecutes.
I am aware about how to handle async calls in nodejs. But I want the callbacks in sequence.
e.g. Though there is a async call in if condition i want to hault the loop, so that I can push value of i in dataSeq and it will result in [1,2,3,4,5] array. I want that sequence because my post operations are dependent on that sequence.
I think asyncjs#eachSeries has what you need.
Your code would become something like this:
async.each(data, (item, callback) => {
if(item%2 == 0){
store.findOne({'visibility': true},function(err, data){
dataSeq.push(i)
i++;
});
}
else{
dataSeq.push(i)
i++;
}
}, (err) => {
// if any of the callbacks produced an error, err would equal that error
});
You can use something like async#eachOf
var async = require('async');
var data = [10,21,33,40,50,69];
var dataSeq = [];
async.eachOf(data, function(value, key, cb) {
if (value % 2 == 0) {
store.findOne({ 'visibility': true })
.then(function(doc) {
dataSeq.push(key);
})
.catch(function(err) {
return cb(err);
});
} else {
cb();
}
}, function(err) {
if (err) {
console.error(err)
return res.status(500).send(); # handle the error as you want
}
return res.status(200).send({ message: 'Task Completed'})
})
I've created a controller that does a bing search based on the user's input into the url. Based on my results from doing a console.log the controller is working correctly and I have set that variable to return. In the route file the information is not displaying to the page. I thought it might be an asynchronous issue so I am trying to use promises to make sure the controller has returned before it tries to do the res.json but I'm not very familiar with promises so my syntax might be off or I might be going about this the wrong way. Will someone take a look at this syntax and see if there is an issue.Currently only an empty object is displaying on the page.
app.route('/imagesearch/:keyword')
.get(function (req, res) {
var resObj = [];
resObj = new Promise (function(resolve, reject){
resolve(bingSearchHandler.findImages(req.params));
});
resObj.then(res.json(resObj));
});
//BINGSEARCHHANDLER
'use strict';
var bingAPPID = 'fwHyQAoJMJYmK8L4a3dIV2GAEUfXAlFRjCnBx0YbfPE=';
var Search = require('bing.search');
var util = require('util');
var search = new Search(bingAPPID);
function bingSearchHandler () {
this.findImages = function(userInput){
var keyword = userInput.keyword;
search.images(keyword,
{top: 10},
function(err, results) {
if(err)
{
console.log(err);
}
else
{
var resArr = [];
(util.inspect(results,
{colors: true, depth: null}));
for(var i=0;i<results.length;i++)
{
var tempObj = {};
tempObj.url = results[i].url;
tempObj.snippet = results[i].title;
tempObj.thumbnail = results[i].thumbnail.url;
tempObj.context = results[i].sourceUrl;
resArr.push(tempObj);
}
console.log(resArr);
return resArr;
}
}
);
}
}
module.exports = bingSearchHandler;
Could you please try this code? Here you have the bing.search documentation, https://www.npmjs.com/package/bing.search Always try to use callbacks instead of promises in NodeJs, remember that the first parameter of a callback is always the error (if there is any), then the response
app.route('/imagesearch/:keyword')
.get(function (req, res) {
bingSearchHandler.findImages(req.params, function (err, response) {
if (err) return res.status(400)
res.json(response)
})
});
//BINGSEARCHHANDLER
'use strict';
var bingAPPID = 'fwHyQAoJMJYmK8L4a3dIV2GAEUfXAlFRjCnBx0YbfPE=';
var Search = require('bing.search');
var util = require('util');
var search = new Search(bingAPPID);
function bingSearchHandler () {
this.findImages = function(userInput, callback){
var keyword = userInput.keyword;
search.images(keyword,
{top: 10},
function(err, results) {
if(err) callback(err)
else
{
var resArr = [];
(util.inspect(results,
{colors: true, depth: null}));
for(var i=0;i<results.length;i++)
{
var tempObj = {};
tempObj.url = results[i].url;
tempObj.snippet = results[i].title;
tempObj.thumbnail = results[i].thumbnail.url;
tempObj.context = results[i].sourceUrl;
resArr.push(tempObj);
}
console.log(resArr);
return callback(null, resArr);
}
}
);
}
}
module.exports = bingSearchHandler;
Something like this should work.
Using callbacks
app.route('/imagesearch/:keyword')
.get(function (req, res) {
// Make the async request, pass the callback function
bingSearchHandler.findImages(req.params, (error, response) => {
if (error === null) {
res.json(response);
}
});
});
Additionally, you'll need to rework your findImages function.
this.findImages = (userInput, callback) => {
var keyword = userInput.keyword;
search.images(keyword, {top: 10}, function (err, results) {
if (err) {
callback(err);
}
else {
var resArr = [];
util.inspect(results, {colors: true, depth: null});
for(var i = 0; i < results.length; i++) {
var tempObj = {};
tempObj.url = results[i].url;
tempObj.snippet = results[i].title;
tempObj.thumbnail = results[i].thumbnail.url;
tempObj.context = results[i].sourceUrl;
resArr.push(tempObj);
}
callback(null, resArr);
}
});
}
Using promises
app.route('/imagesearch/:keyword')
.get(function (req, res) {
// Make the async request, pass the callback function
bingSearchHandler.findImages(req.params).then(response =>
res.json(response);
});
});
// Images function
this.findImages = (userInput) => {
return new Promise((resolve, reject) => {
var keyword = userInput.keyword;
search.images(keyword, {top: 10}, function (err, results) {
if (err && typeof reject === 'function') {
reject(err);
}
else {
var resArr = [];
util.inspect(results, {colors: true, depth: null});
for(var i = 0; i < results.length; i++) {
var tempObj = {};
tempObj.url = results[i].url;
tempObj.snippet = results[i].title;
tempObj.thumbnail = results[i].thumbnail.url;
tempObj.context = results[i].sourceUrl;
resArr.push(tempObj);
}
if (typeof resolve === 'function') {
resolve(resArr);
}
}
});
});
}
waterfall function with two calls but the second on is not waiting for the first one to completely finish. The first one has a mongodb.find() call in it.
Here is the async-waterfall function
app.get("/news", function(req, res) {
async.waterfall([
function (callback) {
var blogs = tendigiEngine.getAllBlogs(callback);
callback(null, blogs);
},
function (blogs, callback) {
var array = tendigiEngine.seperateBlogs(blogs, callback);
callback(null, array );
}
], function (err, result) {
// result now equals 'done'
console.log("done");
console.log(result);
});
});
Here are the two functions being called:
getAllBlogs():
exports.getAllBlogs = function() {
Blog.find(function(err, theBlogs){
if(!err) {
return theBlogs;
}
else {
throw err;
}
});
}
seperateBlogs():
exports.seperateBlogs = function(blogs) {
if(blogs.length === 0 ) {
return 0;
}
else {
blogs.reverse();
var blog = blogs[0];
blogs.shift();
var finArray = [blog, blogs];
return finArray;
}
console.log("asdf");
}
It is important that seperateBlogs won't be called before getAllBlogs() has returned theBlogs, but it is being called before the value is returned. I used Async_Waterfall to avoid this problem but it keeps recurring, which means I am using it wrong. What am I doing wrong here and how can I fix it?
Thanks!
Your exported functions are missing the callback parameters:
exports.getAllBlogs = function(cb) {
Blog.find(cb);
};
exports.seperateBlogs = function(blogs, cb) {
if (blogs.length === 0 )
return cb(null, blogs);
blogs.reverse();
var blog = blogs[0];
blogs.shift();
cb(null, [blog, blogs]);
}
Then your main code can be simplified as well:
async.waterfall([
tendigiEngine.getAllBlogs,
tendigiEngine.seperateBlogs
], function (err, result) {
// result now equals 'done'
console.log("done");
console.log(result);
});