I've been having this weird issue with an application I'm building. Essentially a function is invoked I want to read in a user's current game statistics -Wins, losses, draws etc - I do this using a service which creates an observable and consumes data from my rest api. On first call of this method the data read in is the most current up to date version but after this point I update the document for the user in the database and then when I execute the function again it reads in the original document before the update. However when I check the database the document has in face been updated.
Here is my provider function for consuming the data.
getUser(id) {
if (this.data) {
return Promise.resolve(this.data);
}
return new Promise(resolve => {
this.http.get('https://pitchlife-hearts.herokuapp.com/api/users/' + id)
.map(res => res.json())
.subscribe(data => {
this.data = data;
resolve(this.data);
});
});
}
Here is the call I make in my function.
play(challenger, opponent) {
this.userService.getUser(_id).then((data) => {
this.challenger_account = {
_id: data._id,
points: data.maroon_points,
wins: data.wins,
draws: data.draws,
losses: data.losses
};
Here is my update call.
this.userService.updateUser(this.challenger_account);
Here is my api endpoint call as well although this does work every time I update the data.
app.post('/api/users/update', function (req, res) {
// Update a user
var options = {};
User.update({_id : req.body._id }, {
maroon_points: req.body.points,
wins: req.body.wins,
draws: req.body.draws,
losses: req.body.losses
}, options,
function (err, user) {
if (err)
res.send(err);
res.json(user);
});
});
Any help with this would be hugely appreciated as this is driving me crazy.
When are you updating the this.data property that the getUser(id) { ... } method uses?
Because the first time the getUser(id) {...} method is executed, this.data is null and because of that the http request is made. But after that, the value of this.data is always returned, but if you don't update it manually, it'll be always the first value it was set to.
Related
Good day everyone, I am working with watermelondb and I have the code below, but I don't know how to actually use it. I am new in watermelondb and I don't know how to pass data as props to the pullChanges and pushChanges objects. How do I pass necessary data like changes and lastPulledAt from the database into the sync function when I call it. And I need more explanation on the migrationsEnabledAtVersion: 1 too. Thanks in advance for your gracious answers.
import { synchronize } from '#nozbe/watermelondb/sync'
async function mySync() {
await synchronize({
database,
pullChanges: async ({ lastPulledAt, schemaVersion, migration }) => {
const urlParams = `last_pulled_at=${lastPulledAt}&schema_version=${schemaVersion}&migration=${encodeURIComponent(JSON.stringify(migration))}`
const response = await fetch(`https://my.backend/sync?${urlParams}`)
if (!response.ok) {
throw new Error(await response.text())
}
const { changes, timestamp } = await response.json()
return { changes, timestamp }
},
pushChanges: async ({ changes, lastPulledAt }) => {
const response = await fetch(`https://my.backend/sync?last_pulled_at=${lastPulledAt}`, {
method: 'POST',
body: JSON.stringify(changes)
})
if (!response.ok) {
throw new Error(await response.text())
}
},
migrationsEnabledAtVersion: 1,
})
}
Watermelondb's documentation is terrible and its link to typescript even worse.
I spent almost a week to get 100% synchronization with a simple table, now I'm having the same problems to solve the synchronization with associations.
Well, the object you need to return in pullChanges is of the following form:
return {
changes: {
//person is the name of the table in the models
person: {
created: [
{
// in created you need to send null in the id, if you don't send the id it doesn't work
id: null,
// other fields of your schema, not model
}
],
updated: [
{
// the fields of your schema, not model
}
],
deleted: [
// is a string[] consisting of the watermelondb id of the records that were deleted in the remote database
],
}
},
timestamp: new Date().getTime() / 1000
}
In my case, the remote database is not a watermelondb, it's a mySQL, and I don't have an endpoint in my API that returns everything in the watermelon format. For each table I do a search with deletedAt, updatedAt or createdAt > lastPulledAt and do the necessary filtering and preparations so that the data from the remote database is in the schema format of the local database.
In pushChanges I do the reverse data preparation process by calling the appropriate creation, update or deletion endpoints for each of the tables.
It's costly and annoying to do, but in the end it works fine, the biggest problem is watermelon's documentation which is terrible.
I'm trying to update my mongodb database in javascript by accessing some documents from the database, changing a specific document and then performing a patch request via axios.
When I get to the patch request I'm able to update the database however the promise is stuck on pending and thus, the then() part of the code is not run.
This is the main structure of the code:
In the first part the documents are requested from the database via axios.get:
function updateDocument(someinputdata){
g = axios.all([axios.get('/getData1),axios.get('/getData2)])
.then(response => {
Data1 = response[0].data;
Data2 = response[1].data;
adjustData(Data1,Data2);
});
}
In the second part a specific document is changed and a patch request is called:
function adjustData(Data1,Data2){
...getting specific document and change value from specific field...
var newRec = {
title: "dummyTitle",
rate: newRateValue
};
promise = axios({
url: '/patch/The Real Title',
method: 'PATCH',
data: newRec,
headers: { "Content-Type": "application/json" }
})
.then(() => {
console.log('I want this text to display but it doesn't')
});
}
If I console.log(promise):
Promise {<pending>}
__proto__: Promise
[[PromiseState]]: "pending"
[[PromiseResult]]: undefined
On the server side I have this:
router.patch('/patch/:title', (req,res) => {
const updatedPost = Model.updateOne(
{ "title": req.params.title},
{ $set: { "rate" : req.body.rate}},
(err, result) => {
if(err) {
console.log(err);
throw err;
}
})
.then(
console.log('This text is displayed');
)
})
I want to use the first then() part to update some HTML
Why is the patch request stuck on pending (so not fulfilled or rejected)?
I've figured out what my problem was.
I needed to add
res.json({msg: "Your data has been saved"});
to the code on the server side.
Say I have a list of models:
const documents = [{}, {}, {}];
And I want to insert these into the DB, or update them all, but only if a condition is met:
Model.update({isSubscribed: {$ne: false}}, documents, {upsert:true},(err, result) => {
});
The above signature is surely wrong - what I want to do is insert/update the documents, where the condition is met.
There is this Bulk API:
https://docs.mongodb.com/manual/reference/method/Bulk.find.upsert/
but I can't tell if it will work when inserting multiple documents.
Imagine this scenario: We have a list of employees and a form of some sorts to give them all a penalty, at once, not one by one :)
On the backend side, you would have your eg addBulk function. Something like this:
Penalty controller
module.exports = {
addBulk: (req, res) => {
const body = req.body;
for (const item of body) {
Penalty.create(item).exec((err, response) => {
if (err) {
res.serverError(err);
return;
}
});
res.ok('Penalties added successfully');
}
}
Then you'll probably have an API on your frontend that directs to that route and specific function (endpoint):
penaltyApi
import axios from 'axios';
import {baseApiUrl} from '../config';
const penaltyApi = baseApiUrl + 'penalty'
class PenaltyApi {
static addBulk(penalties) {
return axios({
method: 'post',
url: penaltyApi + '/addBulk',
data: penalties
})
}
}
export default PenaltyApi;
...and now let's make a form and some helper functions. I'll be using React for demonstration, but it's all JS by the end of the day, right :)
// Lets first add penalties to our local state:
addPenalty = (event) => {
event.preventDefault();
let penalty = {
amount: this.state.penaltyForm.amount,
unit: this.state.penaltyForm.unit,
date: new Date(),
description: this.state.penaltyForm.description,
employee: this.state.penaltyForm.employee.value
};
this.setState(prevState => ({
penalties: [...prevState.penalties, penalty]
}));
}
Here we are mapping over our formData and returning the value and passing it to our saveBulkEmployees() function
save = () => {
let penaltiesData = Object.assign([], this.state.penalties);
penaltiesData.map(penal => {
penal.employeeId = penal.employee.id;
delete penal.employee;
return penaltiesData;
});
this.saveBulkEmployees(penaltiesData);
}
...and finally, let's save all of them at once to our database using the Bulk API
saveBulkEmployees = (data) => {
PenaltyApi.addBulk(data).then(response => {
this.success();
console.log(response.config.data)
this.resetFormAndPenaltiesList()
}).catch(error => {
console.log('error while adding multiple penalties', error);
throw(error);
})
}
So, the short answer is YES, you can absolutely do that. The longer answer is above :) I hope this was helpful to you. If any questions, please let me know, I'll try to answer them as soon as I can.
I am a beginner with Node.js and Mongoose. I spent an entire day trying to resolve an issue by scouring through SO, but I just could not find the right solution. Basically, I am using the retrieved values from one collection to query another. In order to do this, I am iterating through a loop of the previously retrieved results.
With the iteration, I am able to populate the results that I need. Unfortunately, the area where I am having an issue is that the response is being sent back before the required information is gathered in the array. I understand that this can be handled by callbacks/promises. I tried numerous ways, but I just haven't been successful with my attempts. I am now trying to make use of the Q library to facilitate the callbacks. I'd really appreciate some insight. Here's a snippet of the portion where I'm currently stuck:
var length = Object.keys(purchasesArray).length;
var jsonArray = [];
var getProductDetails = function () {
var deferred = Q.defer();
for (var i = 0; i < length; i++) {
var property = Object.keys(purchasesArray)[i];
if (purchasesArray.hasOwnProperty(property)) {
var productID = property;
var productQuery = Product.find({asin:
productQuery.exec(function (err, productList) {
jsonArray.push({"productName": productList[0].productName,
"quantity": purchasesArray[productID]});
});
}
}
return deferred.promise;
};
getProductDetails().then(function sendResponse() {
console.log(jsonArray);
response = {
"message": "The action was successful",
"products": jsonArray
};
res.send(response);
return;
}).fail(function (err) {
console.log(err);
})
});
I am particularly able to send one of the two objects in the jsonArray array as the response is being sent after the first element.
Update
Thanks to Roamer-1888 's answer, I have been able to construct a valid JSON response without having to worry about the error of setting headers after sending a response.
Basically, in the getProductDetails() function, I am trying to retrieve product names from the Mongoose query while mapping the quantity for each of the items in purchasesArray. From the function, eventually, I would like to form the following response:
response = {
"message": "The action was successful",
"products": jsonArray
};
where, jsonArray would be in the following form from getProductDetails :
jsonArray.push({
"productName": products[index].productName,
"quantity": purchasesArray[productID]
});
On the assumption that purchasesArray is the result of an earlier query, it would appear that you are trying to :
query your database once per purchasesArray item,
form an array of objects, each containing data derived from the query AND the original purchasesArray item.
If so, and with few other guesses, then the following pattern should do the job :
var getProductDetails = function() {
// map purchasesArray to an array of promises
var promises = purchasesArray.map(function(item) {
return Product.findOne({
asin: item.productID // some property of the desired item
}).exec()
.then(function product {
// Here you can freely compose an object comprising data from :
// * the synchronously derived `item` (an element of 'purchasesArray`)
// * the asynchronously derived `product` (from database).
// `item` is still available thanks to "closure".
// For example :
return {
'productName': product.name,
'quantity': item.quantity,
'unitPrice': product.unitPrice
};
})
// Here, by catching, no individual error will cause the whole response to fail.
.then(null, (err) => null);
});
return Promise.all(promises); // return a promise that settles when all `promises` are fulfilled or any one of them fails.
};
getProductDetails().then(results => {
console.log(results); // `results` is an array of the objects composed in getProductDetails(), with properties 'productName', 'quantity' etc.
res.json({
'message': "The action was successful",
'products': results
});
}).catch(err => {
console.log(err);
res.sendStatus(500); // or similar
});
Your final code will differ in detail, particularly in the composition of the composed object. Don't rely on my guesses.
I've been struggling with this for the past hour. I can't get it to work. In my saga I have a simple call to get some data from local mongo database for react native (https://github.com/smartdemocracy/react-native-local-mongodb) and then dispatch it with put().
let day = yield call(getDay, payload.day.date);
yield put({ type: 'UPDATE_DAY', payload:{day:payload.day,index:payload.index,} })
This is the API call I make :
return db.findOne({ _id: date }, function (err, doc) {
return doc;
});
It's my understanding that the call function expects a returned Promise, but I'm not even sure if what I have is really one.
So you have your saga like this :
let day = yield call(getDay, payload.day.date);
yield put({ type: 'UPDATE_DAY', payload:{day:payload.day,index:payload.index,} })
Then we'll create a function getDay that could be like
const getDay = (date) => {
return new Promise((resolve, reject) => {
db.findOne({ _id: date , function (err, doc) {
if(err) reject(err)
else resolve(doc)
})
}
}
As you can see we just wrap our function in a Promise, and use resolve/reject to get the result of the yield call.
For the record, you should wrap your yield in a try/catch, and in case the reject is triggered it would run the catch section