I am sort of new to NodeJS and I'm learning as I code but I can't wrap my head around Promise/then.
Here is the piece of code - I'm using a library function to Read database values.
var collection = 'Students';
var query = {};
query.name = 'name';
//readFromDatabse returns -{Function} a promise to return the document found, or null if not found
var temp = readFromDatabase(collection, query).then(function(studentData) {
var result = {
resultDetails: {
username: studentData.username,
password: studentData.password
}
};
return callback(null,resultDetails);
});
but when I read see the values in temp, it contains {"isFulfilled":false,"isRejected":false}!! how can I get the result details into temp?
You have to think of Promises as containers for values. readFromDatabase returns such a container, which might eventually hold the requested value unless the query fails. Your temp variable points to the container, but not the response. The properties isFullfilled and isRejected are attributes of the Promise telling you that it has neither been resolved with a value or rejected with an error.
To get to the response you have to use the then method. The function you register there will be called for you, when the query yields a result or an error.
var collection = 'Students';
var query = {};
query.name = 'name';
var temp = null;
readFromDatabase(collection, query).then(function(studentData) {
var result = {
resultDetails: {
username: studentData.username,
password: studentData.password
}
};
temp = result;
});
// temp is still null here
Related
My goals are to obtain the users nickname by using their ID.
Their ID's are stored as variables which are being collected from a reaction collector.
I have tried a few methods and failed, most of which either return nothing or errors.
The below code returns nothing, the getnames() function is empty. This method was recommended to me buy 2 people from a nodejs discord server which aims to help solve issues, similar to here.
// returns player ID's
function getPlayers() {
let players = [];
players.push(queue.tank[0]); // First (1) in TANK queue
players.push(queue.heal[0]); // First (1) in HEAL queue
players.push(queue.dps[0]); // First (2) in DPS queue
players.push(queue.dps[1]);
return players;
}
// get nick names from ID's
function getnames() {
let players = getPlayers();
let playerNicks = [];
let newPlayer = "";
players.forEach(async player => {
newPlayer = await message.guild.members.fetch(player).then(function (user) {return user.displayName });
playerNicks.push(newPlayer)
return playerNicks;
})}
//formats nicknames into string
function formatnicknames() {
let formatted_string2 = '';
let playerNicks = getnames();
if (playerNicks)
formatted_string2 = `${playerNicks[0]} \n${playerNicks[1]} \n${playerNicks[2]} \n${playerNicks[3]}`;
return formatted_string2;
}
I have also tried a few variations of the below code, still unable to obtain nickname.
message.guild.members.cache.get(user.id)
Edit #1
now tried the following code with no success. (boost1ID contains the ID of 1 user)
var mem1 = message.guild.members.fetch(boost1ID).nickname
Edit #2
tried a new method of obtaining displayname from ID.
var guild = client.guilds.cache.get('guildid');
var mem1 = guild.member(boost1ID);
var mem2 = guild.member(boost2ID);
var mem3 = guild.member(boost3ID);
var mem4 = guild.member(boost4ID);
var nickname1 = mem1 ? mem1.displayName : null;
var nickname2 = mem2 ? mem2.displayName : null;
var nickname3 = mem3 ? mem3.displayName : null;
var nickname4 = mem4 ? mem4.displayName : null;
var Allnicknames = `${nickname1} ${nickname2} ${nickname3} ${nickname4}`
message.channel.send(`testing nicknames: ${Allnicknames}`)
I managed to only return my own name since i dont have a nickname on this server, but the other three users who does have a nickname returned null.
This is the simplest solution:
// your users ids
const IDs = [ '84847448498748974', '48477847847844' ];
const promises = IDs.map((userID) => {
return new Promise(async (resolve) => {
const member = message.guild.member(userID) || await message.guild.members.fetch(userID);
resolve(member.displayName || member.user.username);
});
});
const nicknames = await Promise.all(promises);
// you now have access to ALL the nicknames, even if the members were not cached!
The members you are trying to get the nicknames of are not necessarily cached, and this fixes that.
I made an example that could help you.
let testUsers = [];
module.exports = class extends Command {
constructor(...args) {
super(...args, {
description: 'Testing.',
category: "Information",
});
}
async run(message) {
function getNicknames(userArr, guild) {
let playerNicks = [];
for(var i = 0; i < userArr.length; i++) {
playerNicks.push(guild.member(userArr[i]).displayName);
}
return playerNicks;
}
let testUser = message.guild.members.cache.get(message.author.id);
testUsers.push(testUser);
let guild = message.guild;
console.log(getNicknames(testUsers, guild));
}
}
I created a function getNicknames that takes in two parameters. The first one is an Array of users (as you get one from your function getPlayers()) and the second one is the guild you are playing in. You need to provide the guild, because every user should be a GuildMember, because you want to use .displayName. I created a user Array outside of my command code, because otherwise there will only be one user in the Array everytime you use the command. Inside of the getNicknames() function I have created a new Array playerNicks that I basically fill with the user nicknames we get from our provided user Array.
Now you have to implement that into your code.
The call of the function getNicknames(), for your code should look like this:
getNicknames(getPlayers(), message.guild);
I am trying to access a key with unknown parent as :
var ref = admin.database().ref("user_contacts/{pushId}").child(event.data.ref.parent.key);
ref.once("value", function(querySnapshot) {
var qVal = querySnapshot.val();
console.log("Query Value:", qVal);
});
Snapshot always return null, data exists for this key under multiple.
{pushId} //push ids are unknown here.
I also tried this:
var ref = admin.database().ref("user_contacts/{pushId}").orderByChild(snapshot.ref.parent.key);
ref.once("value", function(querySnapshot) {
var qVal = querySnapshot.val();
console.log("Query Value:", qVal);
});
but same response.
Is there any else way to achieve this? Or any body here can suggest an improvement in my method? I am just trying to search a key in the database.
I am trying to run a PostgreSQL query with Knex and then use the results to run another query.
exports.buildBuoyFeaturesJSON = function (conditionA, conditionB) {
var query = null;
var selectedFields = knex.select
(
knex.raw('t_record.id AS id'),
...
knex.raw('t_record.latitude AS latitude'),
knex.raw('t_record.longitude AS longitude')
)
.from('t_record')
.then(function (response) {
var geometry_array = [];
var rows = response.rows;
var keys = [];
for (var key = 0; key <= rows.length - 1; key++) {
var geometry =
{
"id" : rows[key].id,
"type" : "Feature",
"geometry" : rows[key].geometry,
"properties" : {
...
"sensors" : []
}
};
keys.push(rows[key].id);
geometry_array.push(geometry);
}
getMeasurementsAndSensors(keys, geometry_array);
});
};
The latter function uses some of the results from the previous function. Due to asynchronous nature of Knex, I need to call the second function from inside the first function's .then() statement:
function getMeasurementsAndSensors (keys, geometry_array) {
var query = knex
.select
(
't_record_id',
'i_sensor_id',
'description',
'i_measurement_id',
't_sensor_name',
't_measurement_name',
'value',
'units'
)
.from('i_record')
...
.whereRaw('i_record.t_record_id IN (' + keys + ')')
.orderByRaw('t_record_id, i_sensor_id ASC')
.then(function (response) {
var rows = response.rows;
var t_record_id = 0;
var i_sensor_id = 0;
var record_counter = -1;
var sensor_counter = -1;
for (var records = 0; records <= rows.length -1; records++) {
if (t_record_id !== rows[records].t_record_id) {
t_record_id = rows[records].t_record_id;
record_counter++;
sensor_counter = -1;
}
if (i_sensor_id !== rows[records].i_sensor_id) {
i_sensor_id = rows[records].i_sensor_id;
geometry_array[record_counter].properties.sensors[++sensor_counter] =
{
'i_sensor_id' : rows[records].i_sensor_id,
't_sensor_name' : rows[records].t_sensor_name,
'description' : rows[records].description,
'measurements' : []
};
}
geometry_array[record_counter].properties.sensors[sensor_counter].measurements.push
({
'i_measurement_id': rows[records].i_measurement_id,
'measurement_name': rows[records].t_measurement_name,
'value': rows[records].value,
'units': rows[records].units
});
}
//wrapping features with metadata.
var feature_collection = GEOGRAPHY_METADATA;
feature_collection.features = geometry_array;
JSONToFile(feature_collection, 'buoy_features');
});
}
Currently I save end result to a JSON file because I couldn't get Promises to work. JSON is later used to power a small OpenLayers application, hence the JSON-ification after getting results.
I am quite sure that getting the data from a database, saving it to file, then accessing it from another process and using it for OpenLayers is a very redundant way to do it, but so far, it is the only one that works.
I know there are a lot of ways to make these functions work better, but I am new to promises and don't know how to work with them outside of most basic functions. Any suggestions how to make this code better are welcome.
All you appear to be missing is a bunch of returns.
Here are skeletonized versions of the two functions, including the necessary returns :
exports.buildBuoyFeaturesJSON = function(conditionA, conditionB) {
return knex.select (...)
^^^^^^
.from(...)
.then(function(response) {
// synchronous stuff
// synchronous stuff
return getMeasurementsAndSensors(keys, geometry_array);
^^^^^^
}).then(function(geometry_array) {
var feature_collection = GEOGRAPHY_METADATA;
feature_collection.features = geometry_array;
return feature_collection;
^^^^^^
});
};
function getMeasurementsAndSensors(keys, geometry_array) {
return knex.select(...)
^^^^^^
.from(...)
...
.whereRaw(...)
.orderByRaw(...)
.then(function(response) {
// heaps of synchronous stuff
// heaps of synchronous stuff
// heaps of synchronous stuff
return geometry_array;
^^^^^^^^^^^^^^^^^^^^^
});
}
I moved the feature_collection collection part into buildBuoyFeaturesJSON() on the basis that it seems to sit there more logically. If not, then it would be very simple to move it back into getMeasurementsAndSensors().
I have not tried to fix the additional issue highlighted by #vitaly-t.
Dears ,
How can i run promises in nodejs sequentially , in the following example am looping through array of hours then for each fetched hour get result from the database , the issue here : am getting results but i want it sequentially same order that i got hours .
angular.forEach(SharedVar.getCategories(), function (h) {
t = h.split('-', 2);
t = t[0];
RESTApi.getAnswerdCallsByHour(t).then(function (answerdTotal) {
$scope.answerdCallsTotalByHour.push(answerdTotal);
var d = SharedVar.getDataS();
d[count] = answerdTotal;
SharedVar.setDataS(d);
count++;
});
});
Thanks ,
var promise = Promise.resolve(); // make an empty promise in the way you do it with your promise library
angular.forEach(SharedVar.getCategories(), function (h) {
promise.then(function() {
return RESTApi.getAnswerdCallsByHour(t).then(function (answerdTotal) {});
});
});
The way to do it sequently would be to do one Request and do the next request inside the promise.
I think the better approach by far is to extend your SharedVar.setDataS(d) function in a way, that it does not depend on getting the data sequentially. Like having a SharedVar.setDataS(d, index) and using the config var in your $http.get (or whatever) functioncall inside your RESTApi to promote that index all the way to the promise.
If your RESTApi looks like this:
var RESTApi = {
getAnswerdCallsByHour : function(hour) {
var url = "bla.com/myservice?hour=" + hour;
return $http.get(url).data;
}
// Some other Methods...
Then you need a way to pass something to "reorder" your Data when it arrives asynchronously, this could be a index you count up or in your case maybe the hour Variable:
var RESTApi = {
getAnswerdCallsByHour : function(hour) {
var url = "bla.com/myservice?hour=" + hour;
var config = [];
config.hour = hour;
return $http.get(url, config); // Return the promise not just data or a specific field
}
// Some other Methods...
Now when your promise is fullfiled you can access your "hour" Variable like so:
var d = SharedVar.getDataS();
d[promise.config.hour] = promise.data;
SharedVar.setDataS(d);
Now you know what piece of data correlates to which request and you do not need to recieve Data in order. The last piece only works properly when hours runs sequential from 0 to 23, if that isn't the case you need to:
var RESTApi = {
getAnswerdCallsByHour : function(hour, index) {
var url = "bla.com/myservice?hour=" + hour;
var config = [];
config.index = index;
return $http.get(url, config);
}
// Some other Methods...
...
...
var d = SharedVar.getDataS();
d[promise.config.index] = promise.data;
SharedVar.setDataS(d);
Safari's answer is how I typically handle this. (Sorry, I don't have enough rep to comment yet...) You were experiencing problems with it because the example provided does not capture and use the new promise in subsequent loops. See my comments on the slightly modified version here:
var promise = Promise.resolve();
angular.forEach(SharedVar.getCategories(), function (h) {
t = h.split('-', 2);
t = t[0];
// You must capture the new promise here; the next loop will wait
// for the promise returned from getAnswerdCallsByHour to resolve.
promise = promise.then(function() {
// Halt downstream promises until this returned promises finishes
return RESTApi.getAnswerdCallsByHour(t).then(function (answerdTotal) {
$scope.answerdCallsTotalByHour.push(answerdTotal);
var d = SharedVar.getDataS();
d[count] = answerdTotal;
SharedVar.setDataS(d);
count++;
});
});
});
Is there a way to stub a virtual attribute of a Mongoose Model?
Assume Problem is a model class, and difficulty is a virtual attribute. delete Problem.prototype.difficulty returns false, and the attribute is still there, so I can't replace it with any value I want.
I also tried
var p = new Problem();
delete p.difficulty;
p.difficulty = Problem.INT_EASY;
It didn't work.
Assigning undefined to Problem.prototype.difficulty or using sinon.stub(Problem.prototype, 'difficulty').returns(Problem.INT_EASY);
would throw an exception "TypeError: Cannot read property 'scope' of undefined", while doing
var p = new Problem();
sinon.stub(p, 'difficulty').returns(Problem.INT_EASY);
would throw an error "TypeError: Attempted to wrap string property difficulty as function".
I am running out of ideas. Help me out! Thanks!
mongoose internally uses Object.defineProperty for all properties. Since they are defined as non-configurable, you can't delete them, and you can't re-configure them, either.
What you can do, though, is overwriting the model’s get and set methods, which are used to get and set any property:
var p = new Problem();
p.get = function (path, type) {
if (path === 'difficulty') {
return Problem.INT_EASY;
}
return Problem.prototype.get.apply(this, arguments);
};
Or, a complete example using sinon.js:
var mongoose = require('mongoose');
var sinon = require('sinon');
var problemSchema = new mongoose.Schema({});
problemSchema.virtual('difficulty').get(function () {
return Problem.INT_HARD;
});
var Problem = mongoose.model('Problem', problemSchema);
Problem.INT_EASY = 1;
Problem.INT_HARD = 2;
var p = new Problem();
console.log(p.difficulty);
sinon.stub(p, 'get').withArgs('difficulty').returns(Problem.INT_EASY);
console.log(p.difficulty);
As of the end of 2017 and the current Sinon version, stubbing only some of the arguments (e.g. only virtuals on mongoose models) can be achieved in the following manner
const ingr = new Model.ingredientModel({
productId: new ObjectID(),
});
// memorizing the original function + binding to the context
const getOrigin = ingr.get.bind(ingr);
const getStub = S.stub(ingr, 'get').callsFake(key => {
// stubbing ingr.$product virtual
if (key === '$product') {
return { nutrition: productNutrition };
}
// stubbing ingr.qty
else if (key === 'qty') {
return { numericAmount: 0.5 };
}
// otherwise return the original
else {
return getOrigin(key);
}
});
The solution is inspired by a bunch of different advises, including one by #Adrian Heine