I am trying to write this code with Promise. but I don't know how to write promise inside Promise and loop.
I tried to think like this but insertBook function become asynchronously.
How can I get bookId synchronously?
update: function(items, quotationId) {
return new Promise(function(resolve, reject) {
knex.transaction(function (t) {
Promise.bind(result).then(function() {
return process１
}).then(function() {
return process２
}).then(function() {
var promises = items.map(function (item) {
var people = _.pick(item, 'familyName', 'firstNumber', 'tel');
if (item.type === 'book') {
var book = _.pick(item, 'name', 'bookNumber', 'author');
var bookId = insertBook(t, book);
var values = _.merge({}, people, {quotation: quotationId}, {book: bookId});
} else {
var values = _.merge({}, people, {quotation: quotationId});
}
return AModel.validateFor(values);
});
return Promise.all(promises);
}).then(function(items) {
var insertValues = items.map(function (item) {
return People.columnize(item);
});
return knex('people').transacting(t).insert(insertValues);
}).then(function() {
return process5
}).then(function() {
...........
}).then(function() {
t.commit(this);
}).catch(t.rollback);
}).then(function (res) {
resolve(res);
}).catch(function(err) {
reject(err);
});
});
}
function insertBook(t, book){
return Promise.bind(this).then(function () {
return Book.columnizeFor(book);
}).then(function (value) {
return knex('book').transacting(t).insert(value, "id");
});
}
You dont need to get bookid synchronously, you can handle it asynchronously correctly. Also, it is possible you want all book insertions happen sequentially, so I refactored the Promise.all part. (done that just to give you an idea. Promise.all should work fine if insertions in parallel are allowed). Furthermore, I think you shouldn't use Promise.bind. To be honest I dont even know what it does, one thing for sure: it doesn't work with standard promises. So here is an example how I think it should work:
update: function(items) {
return new Promise(function(resolve) {
knex.transaction(function (t) {
resolve(Promise.resolve().then(function() {
return process1;
}).then(function() {
return process2;
}).then(function() {
var q = Promise.resolve(), results = [];
items.forEach(function (item) {
q = q.then(function() {
var book = _.pick(item, 'name', 'bookNumber', 'author');
return insertBook(t, book);
}).then(function(bookId) {
var people = _.pick(item, 'familyName', 'firstNumber', 'tel');
var values = _.merge({}, people, {book: bookId});
return AModel.validateFor(values);
}).then(function(item) {
results.push(item);
});
});
return q.then(function() {
return results;
});
}).then(function(items) {
return process4
}).then(function() {
t.commit(result);
}).catch(function(e) {
t.rollback(e);
throw e;
}));
});
});
}
function insertBook(t, book){
return Promise.resolve().then(function () {
return Book.columnizeFor(book);
}).then(function (value) {
return knex('book').transacting(t).insert(value, "id");
});
}
Assuming that insertBook returns a promise you could do
var people = _.pick(item, 'familyName', 'firstNumber', 'tel');
if (item.type === 'book') {
var book = _.pick(item, 'name', 'bookNumber', 'author');
return insertBook(t, book)
.then(bookId => _.merge({}, people, {quotation: quotationId}, {book: bookId}))
.then(AModel.validateFor)
} else {
return Promise.resolve(_.merge({}, people, {quotation: quotationId}))
.then(AModel.validateFor)
}
Related
In c# I would write something like this:
bool HasRole(string userName, string[] groupNames)
{
var ad = new ActiveDirectory();
return groupsNames.Any(groupName => ad.IsUserInGroup(userName, groupName);
}
and then just
if (HasRole("UserName", new[] {"group1", "group2"}))
//do something
in javascript it looks like all things are doing asynchronously, I've read about promises and so on, and tried this:
const ActiveDirectory = require('activedirectory2');
const Promise = require('promise');
const globals = require('./globals');
const activeDirectory = new ActiveDirectory(globals.AdConfig);
hasRole(msg, ...groupNames) {
if (groupNames == null || groupNames == undefined || groupNames.length == 0)
return false;
let promises = [];
groupNames.forEach(groupName => {
let promise = new Promise((resolve, reject) => {
activeDirectory.isUserMemberOf(msg.envelope.user.name, groupName, function (err, isMember) {
if (err) {
reject(err)
}
resolve(isMember);
});
});
promises.push(promise);
});
//I don't clearly understand how I can return promise result only or promise with the right result
let hasRole = false;
promises.forEach(promise => promise.done(result => {
if (result)
hasRole = result;
}));
return hasRole;
So how can write something like:
if (hasRole(msg, 'group1', 'group2'))
//do something...
I suppose I should return promise but how I can do it if i need to check multiple groups?
UPDATE
I wrapped the forEach loop in promise:
return new Promise((resolve, reject) => {
promises.forEach(promise => promise.done(result => {
if (result)
return resolve(result);
}));
and then:
hasRole(msg, 'group1', 'group2').done(result => {
if (result)
//do...
});
May there is another way?
Found a solution. Promises.all is what i needed.
Result code:
hasRole(msg, ...groupNames) {
let promises = [];
groupNames = groupNames.filter(x => x.trim().length > 0);
if (groupNames == undefined || groupNames.length == 0)
{
promises.push(new Promise.resolve(false));
return Promise.all(promises);
}
groupNames.forEach(groupName => {
let promise = new Promise((resolve, reject) => {
activeDirectory.isUserMemberOf(msg.envelope.user.name, groupName, function (err, isMember) {
if (err) {
reject(err)
}
resolve(isMember);
});
});
promises.push(promise);
});
return Promise.all(promises);
}
I have an API call with a forEach loop which I need to be finished before another function is called. It looks like this:
var getTypes = function() {
var stations = [];
stationservice.getCount('/stations')
.then(succCB, errorCB);
function succCB(data) {
data.data.forEach(function(station) {
stations.push({
id: station._id,
})
})
};
// This should only be called once the forEach Loop is done
processStations(stations);
}
I can't find an understandable example of how I can make sure the processStations() gets called once the loop is done. How can I create a promise for this such that it does what I want to achieve?
As soon as you use promises you have to chain everything that depends on that promise (or use await and async if your environment supports it):
function getTypes() {
return stationservice.getCount('/stations')
.then(function(data) {
var stations = [];
data.data.forEach(function(station) {
stations.push({
id: station._id,
})
})
return stations;
})
.then(processStations);
}
And you should return the Promise chain from your getTypes at least if the getTypes should return something that depends on the stationservice.getCount.
Instead of the forEach you might want to use map because this is what you actually do:
function getTypes() {
return stationservice.getCount('/stations')
.then(function(data) {
return data.data.map(function(station) {
return {
id: station._id,
};
})
})
.then(processStations);
}
If you want a "modern code" answer
var getTypes = function() {
return stationservice.getCount('/stations')
.then(data => data.data.map(({_id: id}) =>({id})))
.then(processStations);
}
this is equal to
var getTypes = function getTypes() {
return stationservice.getCount('/stations').then(function (data) {
return data.data.map(function (_ref) {
return { id: _ref._id };
});
}).then(processStations);
};
Though, since the map isn't asynchronous at all
const getTypes = () => stationservice.getCount('/stations').then(data => processStations(data.data.map(({_id: id}) =>({id}))));
is just fine - and in pre modern browser
var getTypes = function getTypes() {
return stationservice.getCount('/stations').then(function (data) {
return processStations(data.data.map(function (_ref) {
return { id: _ref._id };
}));
});
};
Using Async library
async.forEach(data.data, function (item, callback){
stations.push({
id: item._id,
})
callback();
}, function(err) {
processStations(stations);
});
I have a service designed which takes some parameter and then loops through input array, and find out which item is empty and then add those to and array and then after $q.all resolved it should give me the array of empty items.
input is array of items
function getElements(inputs) {
var elements= [],
promise, whenPromise,
promises = [],
mainPromise = $q.defer();
if (inputs.length === 0) {
mainPromise.resolve(elements);
return mainPromise.promise;
}
angular.forEach(inputs, function (input) {
promise = getPromises(input);
whenPromise = $q.resolve(promise).then(function (response) {
$timeout(function() {
if (response.isEmpty) {
**//perform action with the response.data;**
}
});
}, function () {
});
promises.push(whenPromise);
});
$q.all(promises).finally(function () {
mainPromise.resolve(outdatedEntities);
});
return mainPromise.promise;
}
function getPromises(input) {
var deferred = $q.defer();
someSerivce.getItemDetails(input.Id).then(function (value) {
if (value === null) {
$timeout(function () {
deferred.resolve({data: input, isEmpty: true});
});
} else {
//have item locally, but need to see if it's current
input.isEmpty().then(function (isEmpty) {
$timeout(function () {
deferred.resolve({data: input, isEmpty: isEmpty});
});
}, function (error) {
deferred.reject(error);
});
}
});
return deferred.promise;
}
Now, the problem is the $q.all is never resolved. Even though all the internal promises are getting resolved.
This should work:
function getElements(inputs) {
var elements = [],
promise, whenPromise,
promises = [],
mainPromise = $q.defer();
if (inputs.length === 0) {
mainPromise.resolve(elements);
return mainPromise.promise;
}
angular.forEach(inputs, function (input) {
promise = getPromises(input);
whenPromise = promise.then(function (response) {
if (response.isEmpty) {
* *//perform action with the response.data;**
}
}, function () {
});
promises.push(whenPromise);
});
return $q.all(promises).finally(function () {
return outdatedEntities;
});
}
function getPromises(input) {
return someSerivce.getItemDetails(input.Id).then(function (value) {
if (value === null) {
return {data: input, isEmpty: true};
} else {
//have item locally, but need to see if it's current
return input.isEmpty().then(function (isEmpty) {
return {data: input, isEmpty: isEmpty};
}, function (error) {
return error;
});
}
});
}
I want to update multiple row to my database. My problem is the promise not return anything. It save successfully but not return anything.
Here sample of my code:
doUpdate: Promise.method(function (data) {
var self = this;
var jsonData = JSON.parse(data);
return Bookshelf.transaction(function (t) {
return _.each(jsonData, function (value, key) {
var queryMatch = {
id: value.id,
id2: value.id2
};
return self.forge(queryMatch)
.fetch({transacting: t})
.then(function (data) {
return data.save({content: value.newValue});
})
.catch(function(error) {
console.log(error)
})
});
});
})
I'm using bluebird promise.
I tried to keep my code as close to yours as possible. I did manage to do what you asked, so take a look if that's something you can use.
doUpdate: Promise.method(function(data) {
var Self = this;
var jsonData = JSON.parse(data);
return bookshelf.transaction(function(t) {
return Promise.each(jsonData, function(value, key) {
var queryMatch = {
id: value.id,
id2: value.id2
};
return new Self(queryMatch).save({
content: value.newValue
}, {
transacting: t,
method: 'update'
});
});
});
})
Let me know if this works for you.
I'm in a scenario where I have to get data from the server in parts in sequence, and I would like to do that with the help of Promises. This is what I've tried so far:
function getDataFromServer() {
return new Promise(function(resolve, reject) {
var result = [];
(function fetchData(nextPageToken) {
server.getData(nextPageToken).then(function(response) {
result.push(response.data);
if (response.nextPageToken) {
fetchData(response.nextPageToken);
} else {
resolve(result);
}
});
})(null);
});
}
getDataFromServer().then(function(result) {
console.log(result);
});
The first fetch is successful, but subsequent calls to server.getData() does not run. I presume that it has to do with that the first then() is not fulfilled. How should I mitigate this problem?
Nimrand answers your question (missing catch), but here is your code without the promise constructor antipattern:
function getDataFromServer() {
var result = [];
function fetchData(nextPageToken) {
return server.getData(nextPageToken).then(function(response) {
result.push(response.data);
if (response.nextPageToken) {
return fetchData(response.nextPageToken);
} else {
return result;
}
});
}
return fetchData(null);
}
getDataFromServer().then(function(result) {
console.log(result);
})
.catch(function(e) {
console.error(e);
});
As you can see, recursion works great with promises.
var console = { log: function(msg) { div.innerHTML += "<p>"+ msg +"</p>"; }};
var responses = [
{ data: 1001, nextPageToken: 1 },
{ data: 1002, nextPageToken: 2 },
{ data: 1003, nextPageToken: 3 },
{ data: 1004, nextPageToken: 4 },
{ data: 1005, nextPageToken: 0 },
];
var server = {
getData: function(token) {
return new Promise(function(resolve) { resolve(responses[token]); });
}
};
function getDataFromServer() {
var result = [];
function fetchData(nextPageToken) {
return server.getData(nextPageToken).then(function(response) {
result.push(response.data);
if (response.nextPageToken) {
return fetchData(response.nextPageToken);
} else {
return result;
}
});
}
return fetchData(0);
}
getDataFromServer().then(function(result) {
console.log(result);
})
.catch(function(e) { console.log(e); });
<div id="div"></div>
Because your then statement doesn't pass a function to handle error cases, requests to the server for data can fail silently, in which case the promise returned by getDataFromServer will never complete.
To fix this, pass a second function as an argument to then, as below:
function getDataFromServer() {
return new Promise(function(resolve, reject) {
var result = [];
(function fetchData(nextPageToken) {
server.getData(nextPageToken).then(function(response) {
result.push(response.data);
if (response.nextPageToken) {
fetchData(response.nextPageToken);
} else {
resolve(result);
}
}).catch(function(error) {
//Note: Calling console.log here just to make it easy to confirm this
//was the problem. You may wish to remove later.
console.log("Error occurred while retrieving data from server: " + error);
reject(error);
});
})(null);
});
}