I want to a lot of request in for loop.This is my network method.
Future postdata<T, F extends ApiResponseFromJson>({
#required T? requestmodel,
#required F? responsemodel,
#required String? path,
}) async {
try {
final response = await dio.post(path!, data: requestmodel);
print(ApiPath.API_URL + path);
if (response.data is List) {
return List<F>.from(
(response.data).map((e) => responsemodel!.fromJson(e)));
}
return responsemodel!.fromJson(response.data);
} on DioError catch (e) {
final errorMessage = DioExceptions.fromDioError(e).toString();
showSnackBarDialog("Hata", errorMessage, const Icon(Icons.error))
};
List<CarModel> carModel=[CarModel(),CarModel(),CarModel()...]
Future<ResponseModel?> postData(int index) async {
responseModel.carModel = carModel[i];
responseModel= await _networkService
.postdata<RequestModel, ResponseModel>(
requestmodel: requestModel,
responsemodel: ResponseModel(),
path: ApiPath.API_DATA_LINK);
return responseModel;
}
_allListModel() async {
for (var i = 0; i < carModel.length; i++) {
differentList.add(await postData(i));
}
I have different list and i need request list of lenght.But in for loop response always waiting the other index. But i dont need wait. Cause networkModel goes to list of lenght different API and i don't know which one result is coming to first.
I want to request in for loop and i don't need to the other index. How can i do ?
This code call all request at once, just remove await and the method then is called when request end:
_allListModel() {
for (var i = 0; i < carModel.length; i++) {
postData(i).then((value) {
differentList.add(value);
});
}
}
You should use Future.wait to wait for multiple futures. You start all of them and then you wait until all are done and add all the results to the list.
Future<void> _allListModel() async {
var futures = <Future<>>[]
for (var i = 0; i < carModel.length; i++) {
futures.add(postData(i));
}
var responses = await Future.wait(futures);
differentList.addAll(responses);
}
Related
I'm trying to get datas from api and add them a list. But at this moment, I see datas i got but I can't get it out of the function. What should i do?
function
List<dynamic> xxx = [];
#override
void initState() {
super.initState();
Future<List<dynamic>> fetchCompanies(List<dynamic> datas) async {
var response = await Dio().get(CompaniesPath().url);
if (response.statusCode == HttpStatus.ok) {
Map<String, dynamic> company = jsonDecode(response.data);
for (int i = 0; i < company['Data'].length; i++) {
datas.add(company['Data'][i]);
}
//print(datas); //=> I see datas here
} else {
throw Exception();
}
return datas;
}
print(fetchCompanies(xxx));
}
When I run print(fetchCompanies(xxx)); I got "Instance of 'Future<List<dynamic>>'". How can i get data inside fetchCompanies to my xxx list?
You're trying to print future instance of List that's why you got
Instance of Future<List>
You have to wait until function finish executing.
Catch here is you can't call wait in initState() so you have to use .then method
try this:
fetchCompanies(xxx)
.then((result) {
print("result: $result");
});
It should already work fine like it is. But you probably want to call a setState to refresh the page. Try this:
#override
void initState() {
super.initState();
Future<List<dynamic>> fetchCompanies(List<dynamic> datas) async {
var response = await Dio().get(CompaniesPath().url);
if (response.statusCode == HttpStatus.ok) {
Map<String, dynamic> company = jsonDecode(response.data);
for (int i = 0; i < company['Data'].length; i++) {
datas.add(company['Data'][i]);
}
//print(datas); //=> I see datas here
setState(() {}); // added this
} else {
throw Exception();
}
return datas;
}
print(fetchCompanies(xxx));
}
The Problem is here that I can't find a list of lists and fetch complete information of other lists from API in flutter using Dio.
void fetchAllIndicatorsList(int ModuleId) async {
try {
isLoading(true);
var indicatorslist = await DioClient.fetchAllIndicators(ModuleId);
if (indicatorslist != null) {
Indicatorslist.clear();
first list ==> IndicatorsChecklist.clear();
Indicatorslist.value = indicatorslist;
for(var i=0; Indicatorslist.length>0; i++){
==> second list IndicatorsChecklist.assignAll(Indicatorslist[i].indicators!.length.obs.toJson());
}
}
} finally {
isLoading(false);
}
}enter link description here
Check out my example of getting lists in Dio
Future getCourses() async {
String endPoint = 'api/courses';
final api = service.getApiClient();
try {
final result = await api!.get(endPoint);
final rawList = result.data["data"] as List;
final list = rawList.map((e) => Course.fromJson(e)).toList();
return list;
} on DioError catch (error) {
return error.response!.data;
}
}
I have a list of userIDs and I want to get a value from the database for each user and write it to a new list. But the for loop doesn't wait for the future and throws the error "Unhandled Exception: RangeError (index): Invalid value: Valid value range is empty: 0"
List userIDs = ["gsdgsgsgda32", "gwerszhgda7h", "fsdgz675ehds"];
Future <dynamic> getList() async {
List items=[];
for (var i = 0; i < userIDs.length; i++) {
items[i] = await getUserItems(userIDs[i]);
}
return items;
}
Future <String?> getUserItems(String? _userID) async {
String? userItem=" ";
final FirebaseApp testApp = Firebase.app();
final FirebaseDatabase database = FirebaseDatabase.instanceFor(app: testApp);
database.ref().child('users').child(_userID!).once().then((pdata) {
userItem = pdata.snapshot.child('item').value as String?;
});
return userItem;
}
This is not problem with future. List items is empty so when you call items[0] = 3; there is no items[0] and you get RangeError. Proper way to add element to list is call items.add(3)
So your code should look like this:
List userIDs = ["gsdgsgsgda32", "gwerszhgda7h", "fsdgz675ehds"];
Future <dynamic> getList() async {
List items=[];
for (var i = 0; i < userIDs.length; i++) {
final item = await getUserItems(userIDs[i]);
items.add(item);
}
return items;
}
Future <String?> getUserItems(String? _userID) async {
String? userItem=" ";
final FirebaseApp testApp = Firebase.app();
final FirebaseDatabase database = FirebaseDatabase.instanceFor(app: testApp);
database.ref().child('users').child(_userID!).once().then((pdata) {
userItem = pdata.snapshot.child('item').value as String?;
});
return userItem;
}
By using .then you are telling dart to continue running and come back when the Future completes.
Instead you should use await inside getUserItems.
You have to fiddle around a bit but here's a suggestion to start with:
Future <String?> getUserItems(String? _userID) async {
String? userItem=" ";
final FirebaseApp testApp = Firebase.app();
final FirebaseDatabase database = FirebaseDatabase.instanceFor(app: testApp);
userItem = (await database.ref().child('users').child(_userID!).once()).snapshot.child('item').value as String?
return userItem;
}
Also using String? for userItem and setting it to " " is a bit of an anti pattern. Since you allow it to be nullable i'd suggest having it as null writing your logic around that.
Try to use it like this
Future <dynamic> getList() async {
List items=[];
userIDs.forEach((item) async {
items.add(await getUserItems(item));
});
return items;
}
I have a Future which returns a map. I then need to use the values of that map to await another future and then return the entire result at the end. The problem is that dart can't await async Map.forEach() methods (see this: https://stackoverflow.com/a/42467822/15782390).
Here is my code:
the debug console shows that the items printed are in the following order:
flutter: getting journal entries
flutter: about to loop through pictures
flutter: getting picture
flutter: returning entries
flutter: [[....]] (Uint8List)
Future<List<JournalEntryData>> getJournalEntries() async {
List<JournalEntryData> entries = [];
print('getting journal entries');
EncryptService encryptService = EncryptService(uid);
await journal.get().then((document) {
Map data = (document.data() as Map);
print('about to loop through pictures');
data.forEach((key, value) async {
print('getting picture');
dynamic pictures = await StorageService(uid).getPictures(key);
print('done getting image');
entries.add(JournalEntryData(
date: key,
entryText: encryptService.decrypt(value['entryText']),
feeling: value['feeling'],
pictures: pictures,
));
});
});
print('returning entries');
return entries;
}
Future getPictures(String entryID) async {
try {
final ref = storage.ref(uid).child(entryID);
List<Uint8List> pictures = [];
await ref.listAll().then((result) async {
for (var picReference in result.items) {
Uint8List? pic = await ref.child(picReference.name).getData();
if (pic == null) {
// TODO make no picture found picture
var url = Uri.parse(
'https://www.salonlfc.com/wp-content/uploads/2018/01/image-not-found-scaled-1150x647.png');
var response = await http.get(url);
pic = response.bodyBytes;
}
pictures.add(pic);
}
});
return pictures;
} catch (e) {
print(e.toString());
return e;
}
}
It's quite annoying to have to use for-loops when you need async behaviour, specially on Maps, because as the other answer shows, that requires you to iterate over entries and then take the key and value out of it like this:
for (final mapEntry in data.entries) {
final key = mapEntry.key;
final value = mapEntry.value;
...
}
Instead of that, you can write a utility extension that does the work for you:
extension AsyncMap<K, V> on Map<K, V> {
Future<void> forEachAsync(FutureOr<void> Function(K, V) fun) async {
for (var value in entries) {
final k = value.key;
final v = value.value;
await fun(k, v);
}
}
}
Then, you can use that like this:
await data.forEachAsync((key, value) async {
...
});
Much better.
Don't mix the use of then and await since it get rather confusing and things are no longer being executed as you think.
Also, the use of forEach method should really not be used for complicated logic like what you are doing. Instead, use the for-each loop. I have tried rewrite getJournalEntries here:
Future<List<JournalEntryData>> getJournalEntries() async {
List<JournalEntryData> entries = [];
print('getting journal entries');
EncryptService encryptService = EncryptService(uid);
final document = await journal.get();
Map data = (document.data() as Map);
print('about to loop through pictures');
for (final mapEntry in data.entries) {
final key = mapEntry.key;
final value = mapEntry.value;
print('getting picture');
dynamic pictures = await StorageService(uid).getPictures(key);
print('done getting image');
entries.add(JournalEntryData(
date: key,
entryText: encryptService.decrypt(value['entryText']),
feeling: value['feeling'],
pictures: pictures,
));
}
print('returning entries');
return entries;
}
And getPictures here. I have only removed the use of then here.
Future getPictures(String entryID) async {
try {
final ref = storage.ref(uid).child(entryID);
List<Uint8List> pictures = [];
final result = await ref.listAll();
for (var picReference in result.items) {
Uint8List? pic = await ref.child(picReference.name).getData();
if (pic == null) {
// TODO make no picture found picture
var url = Uri.parse(
'https://www.salonlfc.com/wp-content/uploads/2018/01/image-not-found-scaled-1150x647.png');
var response = await http.get(url);
pic = response.bodyBytes;
}
pictures.add(pic);
}
return pictures;
} catch (e) {
print(e.toString());
return e;
}
}
I have a String List in my shared preferences that's meant to store account numbers which can then be used to make a call from the API:
List<String> accountList = [];
Future _getListData() async {
SharedPreferences myPrefs = await SharedPreferences.getInstance();
for(var i = 0; i < myPrefs.getStringList('accounts').length; i++){
accountList.add(myPrefs.getStringList('accounts')[i]);
}
//prints values from shared preferences
print(accountList);
}
Future<List<dynamic>> fetchData() async {
_getListData();
//prints an empty list
print(accountList);
try {
if (accountList == null) {
var result = await http.get(apiUrl);
List<dynamic> accountInfo = (json.decode(result.body));
return accountInfo;
} else {
List<dynamic> accountInfo = [];
for(var i = 0; i < accountList.length; i++){
var result =
await http.get(apiUrl + "/api/Data/GetCustomer?accntnum=" + accountList[i]);
accountInfo.add(json.decode(result.body));
}
return accountInfo;
}
} catch (e) {
print(e);
}
}
When calling the Future function "fetchData()" from my FutureBuilder in the widget it returns an empty list. However within the scope of the "_getListData()" function it prints the list witht he appropriate values. How can I make it such that "fetchData()" gets the intended list?
Just add an await before _getListData() here:
Future<List<dynamic>> fetchData() async {
await _getListData();
//prints an empty list
print(accountList);