Can anyone help me understand this piece of code:
String? userName = "";
String? userEmail = "";
AuthService authService = AuthService();
#override
void initState() {
// TODO: implement initState
super.initState();
gettingUserData();
}
while defining gettingUserData(), using async, await needs hotreload to show the email
gettingUserData() async {
setState(() async {
userName = await HelperFunction.getUsername();
userEmail = await HelperFunction.getUseremail();
});
}
But defining it using .then doesn't need hot relaod
gettingUserData() {
HelperFunction.getUseremail().then((value) {
setState(() {
userEmail = value;
});
});
HelperFunction.getUsername().then((value) {
setState(() {
userName = value;
});
});
}
Can anyone help me understand why this is?
The two versions are not equivalent. The Future.then version calls setState after each Future completes.
The await version calls setState with an asynchronous callback, which setState does not expect. Since setState expects a VoidCallback argument, it expects its callback to complete synchronously, and it will not be awaited. setState therefore executes and returns immediately before waiting for either of the Futures complete.
One way to correct your await version is to await the Futures first and to then call setState:
Future<void> gettingUserData() async {
var userName = await HelperFunction.getUsername();
var userEmail = await HelperFunction.getUseremail();
setState(() {
this.userName = userName;
this.userEmail = userEmail;
});
}
Related
I have these methods, for some reason fetchItems is being called first before initPosition, how come dart wont wait for it to finish and proceeds to the second method? I've added async/await but it still doesn't work. I've also checked my backend logs to confirm this. Am I doing something wrong?
Future<void> initPosition() async {
if (_latitude != null && _longitude != null) {
await Socket.updatePosition(
lat: 51,
lon: 17,);
}
}
Future<void> initMarkers() async {
await initPosition();
await Provider.of<Items>(context, listen: false)
.fetchItems();
}
void initMapState() async {
await getCurrentLocation().then((_) async {
await initMarkers();
setState(() {
_loaded = true;
});
});
}
#override
void initState() {
super.initState();
_location.enableBackgroundMode(enable: false);
WidgetsBinding.instance?.addPostFrameCallback((_) {
initMapState();
});
}
Future<void> fetchItems() async {
itemList = await repository.getItemList();
notifyListeners();
}
Working with multiple asynchronous functions inside Futures depends on whether one is finished or not, not every single one. For this, you can call the "whenComplete" method so you can assure that your future function have finished running. Like this:
For your initMarkers() function:
Future<void> initMarkers() async {
await initPosition().whenComplete((){
Provider.of<Items>(context, listen: false)
.fetchItems();
});
}
For your initMapState() function:
void initMapState() async {
await getCurrentLocation().whenComplete(() async {
await initMarkers().whenComplete((){
setState(() {
_loaded = true;
});
});
});
}
Keep in mind that, in your code, you are not working with the returning value of your getCurrentLocation() function, so instead of using the "then" method use the "whenComplete" method, assuring that you changed or returned your values with this function. Finally, for the initState(), make the function body with asynchronous:
#override
void initState() {
super.initState();
_location.enableBackgroundMode(enable: false);
WidgetsBinding.instance?.addPostFrameCallback((_) async {
initMapState();
});
}
This should work.
I'm trying to get the return value in my function but the output is 'Instance of Future' instead of the value of school field name in the database
#override
void initState() {
userId = _auth.currentUser!.uid;
publisherSchool =
getName(widget.postInfo['publisher-Id'], 'school').toString();
super.initState();
}
Future getName(String publisherUid, String fieldname) async {
DocumentSnapshot publisherSnapshot = await FirebaseFirestore.instance
.collection('users')
.doc(publisherUid)
.get();
print(publisherSnapshot.get(fieldname));
return publisherSnapshot.get(fieldname);
}
but whenever i'm printing the publisherSnapshop.get(fieldname) i'm getting the correct value from the database
There are 2 ways to do it, you can create a Future method and call it inside the initState like below:
#override
void initState() {
initial();
super.initState();
}
Future<void> initial() async {
userId = _auth.currentUser!.uid;
// Remember using `()` to wrap the `await` to get it result
publisherSchool = (await getName(widget.postInfo['publisher-Id'], 'school')).toString();
}
Or you can use .then to call it directly inside the initState:
#override
void initState() {
userId = _auth.currentUser!.uid;
getName(widget.postInfo['publisher-Id'], 'school').then((value) {
publisherSchool = value.toString();
});
super.initState();
}
When you declare the getName() function, specify the return type as Future<String>, and then when you call getName(), you need to await the result e.g. publisherSchool = await getName(widget.postInfo['publisher-Id'], 'school').toString();
The reason why you are not getting the correct response is because whenever you are working with Futures it takes some time to finish and return the results. Meanwhile it is fetching the result you have to make it await so that the program will continue once that future function is complete since await/then is nowhere to be found in your code hence the issues.
To solve this make this change:
Change
publisherSchool =
getName(widget.postInfo['publisher-Id'], 'school').toString();
To
getName(widget.postInfo['publisher-Id'],
'school').then((value){
publisherSchool=value.toString()});
My issue is, when the page is opened my variable isn't set. So when i'm querying from firestore i get the error The method '[]' was called on null. Receiver: null Tried calling: []("userbio")
I declared 2 variables
var userid;
var useremail;
Then i wrote this future
Future getUserData() async {
var firestore = Firestore.instance;
final FirebaseUser user = await FirebaseAuth.instance.currentUser();
final String uid = user.uid.toString();
final String email = user.email.toString();
DocumentReference qn = await firestore
.collection("users")
.document(email)
.collection('userdetails')
.document(uid);
void initState() {
setState(() {
userid = uid;
useremail = email;
});
}
return qn.documentID;
}
This is how i'm currently trying to setState but it's not working
void initState() {
setState(() {
userid = uid;
useremail = email;
});
}
Please help, thanks.
comment if you need more context
Seems like you're declaring the nested function initState() but you're not calling it. I would just remove the function and call setState() directly :
...
.document(uid);
setState(() {
...
EDIT : Call getUserData() inside initState :
// In a class extending State<T>
#override
void initState() {
super.initState();
// synchronous call if you don't care about the result
getUserData();
// anonymous function if you want the result
() async {
var result = await getUserData();
}();
}
PS : initState(), like build() or setState(), is a predefined name in Flutter. Try not to use those names for functions that are not overriding the original ones.
Try assign your variable an empty value instead of leaving it null.
var userid = '';
var useremail = '';
I'm having an issue trying to call a document from Firestore in initState. I can pull data from a StreamBuilder just fine, but I just want to call the data once on initState.
Here is what I'm doing:
class _PainLevelState extends State<PainLevel> {
final FirebaseAuth _auth = FirebaseAuth.instance;
final CollectionReference userCollection =
Firestore.instance.collection('users');
static final now = DateTime.now();
String _uid;
double myPainLevel = 0;
Future<void> getCurrentUser() async {
final FirebaseUser user = await _auth.currentUser();
if (mounted) {
setState(() {
_uid = user.uid;
});
}
}
Future<void> getCurrentPainLevel() async {
await userCollection
.document(_uid)
.collection('pain')
.where('time',
isGreaterThanOrEqualTo: DateTime(now.year, now.month, now.day))
.getDocuments()
.then((QuerySnapshot docs) {
if (docs.documents.isNotEmpty) {
print('yes');
} else {
print('no');
}
});
}
#override
void initState() {
super.initState();
getCurrentUser();
getCurrentPainLevel();
}
...
I just get a "no" every time I print to console. It's not get any documents when there is one. If I take the same code inside the future and put it somewhere else, like in the build method, it works, but it constantly builds and I don't want that. Any suggestion as to why it is not working? Thanks in advance.
I'm guessing here that your code will not always work, because getCurrentPainLevel might get called before getCurrentUser is completed, which will cause _uid to be null and therefore, not work as expected. Try to put then keyword after getCurrentUser method, like this:
#override
void initState() {
super.initState();
getCurrentUser().then((_) {
getCurrentPainLevel();
});
}
By the way, you should NOT be calling async methods in initState. Try to put the code somewhere else, like WidgetsBinding.instance.addPostFrameCallback(...).
I have to initialise the state of widget variable with the value stored in StoredProcedure.
void initState() {
widget.query = fetchMake();
super.initState();
}
Future<String> fetchMake() async{
final prefs = await SharedPreferences.getInstance();
return prefs.getString(key);
query.toString();
}
But the issue is that it cant assign that value to query variable and showing error value to type future string cannot assign to string flutter
How can I do that?
fetchMake is async so you have to put await where you call that method but it will not work because you are calling it in initState.
So You have to assign widget.query variable value in that function only. Moreover, as you get data you have to call setState, so data you receive reflect in ui.
In addition to that you have to check query is null or not where you are using it because when first time build method call it will not have any data.
String query;
void initState() {
fetchMake();
super.initState();
}
fetchMake() async{
final prefs = await SharedPreferences.getInstance();
setState((){
query = prefs.getString(key) ?? 'default';
});
}
You can try:
String query;
void initState() {
super.initState();
fetchMake().then((value) {
setState(() {
query = value;
});
});
}
Future<String> fetchMake() async{
final prefs = await SharedPreferences.getInstance();
return prefs.getString(key);
}
1, You can not set state with widget.query.
2, Create a variable query on state of Widget.
3, fetchMake is a async function => using then to wait result.