I'm trying to display Firestore data in a Flutter app. To do that, I created a Firebase function like the following:
exports.getHouses = functions.https.onCall((data, context) => {
let pathBeginning = "users/";
console.log(data.userID);
let path = pathBeginning.concat(data.userID, "/houses");
let houses = [];
admin.firestore().collection(path).get().then(snapshot => {
console.log("COLECTION WHERE DOCUMENTS ARE RETREIVED:");
console.log(path);
snapshot.forEach(doc => {
let newHouse = {
"id": doc.id,
"address": doc.data().address
}
houses = houses.concat(newHouse);
});
console.log("THE FOLLOWING LOG SHOULD RETURN THE FULL LIST OF HOUSES:")
console.log(houses);
return houses;
}).catch(reason => {
response.send(reason);
});
});
I think this part works properly, because logs in Firebase look exactly as expected:
Firebase logs
The problem happens when I try to print this data in my Flutter app. To do so, I use the following code:
Future<void> listHouses() async {
var parameters = {
"userID": "1"
};
HttpsCallable getHouses = FirebaseFunctions.instance.httpsCallable("getHouses");
await getHouses.call(parameters).then((HttpsCallableResult response) {
print(response.data);
});
}
When called the funtion, it always returns null, even when Firebase log displays everything properly.
I would appreciate if anyone can help me solving this issue. Thank you in advance.
You're missing a return in front of your get() call. Without that, the Cloud Functions container doesn't know about the asynchronous get() operation and thus will/may terminate the function before loading the data completes.
To fix this, add return:
return admin.firestore().collection(path).get().then(snapshot => {
...
This is an extremely common problem within Cloud Functions and when dealing with asynchronous APIs in general, so I recommend taking a moment to read the Firebase documentation on terminating functions and watching the video series linked in there.
Related
I'm stuck with a situation where I am trying to use a RiverPod provider in my Flutter app to represent user preference data. In this case, the user preference data is stored in FireStore.
I'm stuck with understanding how to load provider state from Firestore. Currently, I'm trying to use the "userPreferencesFutureProvider" to load the 'GdUserPreferences" data from a service that calls Firestore, which then pushes the data into "userPreferencesProvider" using the 'overrideWith' method. However, when I access the user preference data via the 'userPreferencesProvider' provider the data loaded from Firestore is not present
final userPreferencesFutureProvider = FutureProvider<bool>( (ref) async {
final p = ref.watch(userPrefsServiceProvider);
GdUserPreferences? aPrefs = await p.load();
if (aPrefs == null) {
aPrefs = GdUserPreferencesUtil.createDefault();
}
userPreferencesProvider.overrideWith((ref) => UserPreferencesNotifier(p,aPrefs!));
return true;
});
final userPreferencesProvider = StateNotifierProvider<UserPreferencesNotifier,GdUserPreferences>((ref) {
return UserPreferencesNotifier(ref.watch(userPrefsServiceProvider),GdUserPreferences());
});
Any suggestions?
Update
Further to the feedback received I have updated my code as shown below, but this still doesn't work...
final userPreferencesFutureProvider = FutureProvider<bool>( (ref) async {
// get service that wraps calls to Firestore
final p = ref.watch(userPrefsServiceProvider);
// load data from Firestore
GdUserPreferences? aPrefs = await p.load();
// if none found then create default values
if (aPrefs == null) {
aPrefs = GdUserPreferencesUtil.createDefault();
}
// push state into a provider that will be used
ref.read(userPreferencesProvider.notifier).update(aPrefs);
// this future returns a boolean as a way of indicating that the data load succeeded.
// elsewhere in the app access to the user preference data is via the userPreferencesProvider
return true;
});
final userPreferencesProvider = StateNotifierProvider<UserPreferencesNotifier,GdUserPreferences>((ref) {
print('default provider');
return UserPreferencesNotifier(ref.watch(userPrefsServiceProvider),GdUserPreferences());
});
class UserPreferencesNotifier extends StateNotifier<GdUserPreferences> {
// service is a wrapper around FireStore collection call
final GdUserPreferencesService service;
UserPreferencesNotifier(this.service, super.state);
void update(GdUserPreferences aNewPrefs) {
print('update state');
state = aNewPrefs;
}
}
The purpose of having a separate FutureProvider and StateNotifierProvider, is that I can insert the FutureProvider when the app first loads. Then when I want to access the user preference data I can use the straight forward StateNotifierProvider, which avoids the complications of having Future Providers all over the app.
Note: using the print methods I can show that the 'update' method is called after the userPreferencesProvider is first created, so I can't understand why the data is not updated correctly
Apologies to all responders...
The problem was caused by a coding error on my side. I had two versions of 'userPreferencesProvider' defined in two different locations. Taking out the rogue duplicate definition and it now works fine.
I am trying to get documents with their own subcollections, from Stream, but I am stuck.
This is where I set up my StreamSubscription:
Future<void> _toggleOrdersHistorySubscription({FirebaseUser user}) async {
_ordersHistorySubscription?.cancel();
if (user != null) {
_ordersHistorySubscription = ordersRepository
.ordersHistoryStream(userId: user.uid)
.listen((ordersSnapshot) {
final List<OrderModel> tmpList = ordersSnapshot.documents.map((e) {
// e.reference.collection("cart").getDocuments().;
return OrderModel.orderFromSnapshot(e);
}).toList();
add(OrdersHistoryUpdated(ordersHistory: tmpList));
});
}
}
The issue is that I can't see a way to get subcollection along with the parent document because getDocuments returns a Future.
Anyone can clear this issue for me?
So, I update the code method a separate method for retrieving data when listener is triggered but it doesn't work fully and I do not understand what's happening and why part of the code is working and part is not.
List<OrderModel> _getOrdersHistory({
#required QuerySnapshot snapshot,
}) {
return snapshot.documents.map((document) {
List<OrderedProductModel> cart = [];
List<AddressModel> addresses = [];
document.reference.collection("cart").getDocuments().then((snapshot) {
snapshot?.documents?.forEach((doc) {
cart.add(OrderedProductModel.fromSnapshot(doc));
});
});
document.reference
.collection("addresses")
.getDocuments()
.then((snapshot) {
snapshot?.documents?.forEach((doc) {
addresses.add(AddressModel.addressFromJson(doc.data));
});
});
final order = OrderModel.orderFromSnapshot(
document,
restaurantCart: cart,
);
return order.copyWith(
orderAddress:
(addresses?.isNotEmpty ?? false) ? addresses.first : null,
sentFromAddress:
(addresses?.isNotEmpty ?? false) ? addresses.last : null,
);
})
.toList() ??
[];
}
As an alternate solution to my original issue is that I made a map entry in Firestore instead of a collection for 2 address documents (which are set above as orderAddress and sentFromAddress) and for the cart I decided to get the data when needed for every cart item.
So the method which I put in the update is not the final one, but I want to understand what is happening up there as I do not understand why:
Why the cart is shown as empty if I do a print(order); right before the return and in the bloc it has data;
Why the orderAddress and sentFromAddress are both empty no matter what I try;
To be short: You'll never be able to get a List synchronously if you get the data async from firebase.
Both questions have the same answer:
Your timeline:
For each document
Create an empty list
Initiate the firebase query - getDocuments()
Subscribe to the returned future with - .then((snapshot){cart.add(...)}).
This lambda will be invoked when the documents arrived.
Another subscribe
Save your empty cart and first/last of empty addresses to an OrderModel
Your List contains the references to your empty lists indirectly
Use your bloc, some time elapsed
Firebase done, your callbacks starts to fill up your lists.
Regarding your comment like stream.listen doesn't like async callbacks:
That's not true, you just have to know how async functions work. They're run synchronously until the first await, then return with an incomplete future. If you do real async things you have to deal with the consequences of the time delay like changed environment or parallel running listeners.
You can deal with parallel running with await for (T v in stream) or you can use subscription.pause() and resume.
If anything returns a future, just do this:
...getDocuments().then((value) => {
value is the item return here. Do something with it....
})
Also, you might want to split your method up a bit to share the responsibility.
If getDocuments is a Future function and you need to wait for it, I think you should add await before it. I also don't see the snapshot status checking in your code pasted here. Maybe you have already checked the snapshot status in other function? Make sure the snapshot is ready when using it.
I'm having some problems with a line in the function below. The function is handling async gets from Firebase Storage. I'm using it to get the names and urls of files I have stored there.
The issues is with getting the Urls. Specifically on the line:
String url = element.getDownloadURL().toString();
getDownloadedURL() is a Firebase future. I tried to await it, but it won't recognise the await, I guess due to "element".
The over all effect is that when I'm using this in my UI via a Future builder, the name comes out fine but the Url doesn't. It is being retrieved as the print statement shows it. But it's not being waited for, so the UI is already updated.
Been trying lots of things, but haven't found a solution, so any help would be greatly appreciated.
Future<void> getImageData() async {
final imagesFromStorage = await fb
.storage()
.refFromURL('gs://little-big-deals.appspot.com')
.child('images')
.listAll();
imagesFromStorage.items.forEach((element) {
print(element.name);
String url = element.getDownloadURL().toString();
print(url.toString());
imageData.add(ImageData(element.name, url.toString()));
});
}
Many thanks
You can't use async in forEach.
Just use a for loop:
Future<void> getImageData() async {
final imagesFromStorage = await fb
.storage()
.refFromURL('gs://little-big-deals.appspot.com')
.child('images')
.listAll();
for (var element in imagesFromStorage.items) {
print(element.name);
String url = (await element.getDownloadURL()).toString();
print(url.toString());
imageData.add(ImageData(element.name, url.toString()));
}
}
I'm trying to query a collection of users using Mongoose in a Node API.
The handler looks like this:
exports.getUsers = async function(req, res, next) {
try {
let users = db.User.find();
return res.status(200).json(users);
} catch(e) {
return next(e);
}
};
This returns an error that reads Converting circular structure to JSON. When I console.log() the results of db.User.find(), I get a Query object. I've checked everything else. All of my other routes are working normally.
Well...I figured it out. I'll post the answer that I discovered in case anyone else is trying to figure this out. It turns out, through a little bit more careful reading of the documentation, that the Query object that is returned has to be executed. There are two ways to execute it - with a callback function or by returning a promise (but not both). I found this page on queries in the mongoose docs helpful. My final handler looked like this.
exports.getUsers = async function(req, res, next) {
try {
db.User.find()
.then(users => {
return res.status(200).json(users);
});
} catch(e) {
return next(e);
}
};
Next time I guess I'll dig around for a few more minutes before asking.
Edit to add:
Found a second solution. Due to the use of the async function, I also was able to use following inside the try block.
let users = await db.User.find();
return res.status(200).json(users);
I am using Redux and trying to make a call to Facebook API with their JS SDK. I've only ever used promises with Redux and so since the method FB.getLoginStatus just returns a simple JS object, I'm not sure how to ensure that the payload doesn't return undefined.
With redux-promise, you add it to the applyMiddleware(ReduxPromise)... and then it ensures nothing is returned until the promise resolves. But I don't know how to do that here.
I've also used async/await functions with React Native without an issue, but I tried using them here and for some reason the code still returns the payload, before the asynchronous request (await ...) is finished. So I tried working with redux-await, but couldn't get it to work.
export function getLoginStatus() {
var res = FB.getLoginStatus(function(res) {
console.log(res);
});
console.log("res ", res);
return {
type: GET_LOGIN_STATUS,
payload: res
}
}
Hm, things can get a little tricky as I've not used redux-promise. And I can't tell exactly what else you have tried. But this would be my first shot:
async function _getLoginStatus() {
var payload = new Promise( (resolve, fail) => {
FB.getLoginStatus((res)=>resolve(res));
});
return {
type: GET_LOGIN_STATUS,
payload: payload
}
}
// Last time I exported an async function I needed this HYMMV
export let getLoginStatus = _getLoginStatus;
And then elsewhere in the code:
import {getLoginStatus} from 'whatever.js';
var payloadResult = await getLoginStatus();