Soo, the title might be a bit confusing but let me clear that up right now.
I have a class called UserController which has a method called updateUserData. It gets a Map<String, dynamic> and updates the given attributes of a user with whatever is given in the value of the map.
What I wanted to do is: Send a patch request to the server, wait for the server to return a changed user object, write that to some local variable and return either the value or the error to whoever called that method (which in my case is a GUI class).
The current method as it is:
Future<User> updateUserData(Map<String, dynamic> changes) async {
return await http.patch(
"url",
headers: {HttpHeaders.authorizationHeader: "token"},
body: changesMap
).then((newUserObject) => {
currentUser = newUserObject;
//return new user object for display
}); //error from server gets forwarded to GUI.
}
Sadly this doesn't work at all. Seems like Flutter/dart doesn't know what to return there (it gives me a return_of_invalid_type_from_closure error).
I hope it's clear what my goal was. I want to use a "then" clause in this method but then still return a future which either contains the user I get from the server or the error I get.
How do I do that? I looked up so many Future tutorials so far and none used something similar.
You never need to use async/await with then. In your case, the simplest thing to do is await the response of your request, and then, put it to your local variable.
Then you just need to return the value.
Future<User> updateUserData(Map<String, dynamic> changes) async {
final response = await http.patch(
"url",
headers: {HttpHeaders.authorizationHeader: "token"},
body: changesMap,
);
// You need to parse the response to get your User object.
final responseJson = json.decode(response.body);
newUserObject = User.fromJson(responseJson);
currentUser = newUserObject;
return newUserObject;
}
If you need to decode your Map to a Class, you can see the answer given here
Related
I am using flutter with the cbl package to persist data. Trying to retrieve the entries does not seem to work because the function created is returning at the await statement and not the return statement. This does not seem like the intended result of darts async/await functionality. So I am lost.
task_database.dart
Future<dynamic> getAllTasks() async {
final tasksDb = await Database.openAsync(database); <---------- Returns here
var tasksQuery = const QueryBuilder()
.select(SelectResult.all())
.from(DataSource.database(tasksDb));
final resultSet = await tasksQuery.execute();
late var task;
await for (final result in resultSet.asStream()) {
final map = result.toPlainMap();
final taskDao = TaskDao.fromJson(map);
task = taskDao.task;
// Do something with the task...
print(task);
}
;
return task; <-------------------------------------------- Does not make it here
}
task_cubit.dart
getAllTasks() => {
allTaskMap = TasksAbcDatabase().getAllTasks(),
emit(TaskState(tasks: state. Tasks))
};
What I have tried. I have tried to use Database.openSync instead of Database.openAsync however, the function just returns at the next await statement. I have also tried making getAllTasks asynchronous and awaiting the database as such.
Future<void> getAllTasks() async => {
allTaskMap = await TasksAbcDatabase().getAllTasks(),
emit(TaskState(tasks: state. Tasks))
};
However this has the same issue, when the function from task_database returns prematurely it the returns at the first await function in getAllTasks which is the allTaskMap variable.
Thanks
A function cannot "return prematurely" without a return statement.
The only way the execution is cut short would be an exception being thrown.
I also don't see how you don't get syntax errors, when you don't await the Database.openAsync(database) statement.
So make sure all your awaits are in place. Use the linter to find those that are missing. While you are at it, remove the keyword dynamic from your vocabulary, it will only hurt you if you use it without a need for it. Your return type should be properly typed, then your compiler could tell you, that returning a single task from a function that is clearly supposed to return multiple tasks is not going to work.
Either catch your exceptions and make sure you know there was one, or do not catch them and watch them go all the way through into your debugger.
In addition, following the comment of #jamesdlin, your function definitions are... valid, but probably not doing what you think they are doing.
Future<void> getAllTasks() async => {
allTaskMap = await TasksAbcDatabase().getAllTasks(),
emit(TaskState(tasks: state. Tasks))
};
needs to be
Future<void> getAllTasks() async {
allTaskMap = await TasksAbcDatabase().getAllTasks();
emit(TaskState(tasks: state. Tasks));
}
I new to Riverpod, and I have a basic question.
On the start up of my app, I make an http to load a preload. This returns a Json response, with basic stings and lists of string, data that is used around the app.
I make the request like this:
class PreLoadApi {
getPreloadList() {
http.get(url,
headers: {HttpHeaders.contentTypeHeader: "application/json", HttpHeaders.authorizationHeader: "Bearer $token"}
).then((http.Response response) {
int statusCode = response.statusCode;
print(statusCode);
log("2124: PreLoad. response.body:${response.body}");
var data = json.decode(response.body);
String name = data['name']
*** Here I want to save the string "name" to a provider. ***
}
Now I want to save this String name in a provider. I would like to make a provider like this:
final nameProvider = StateProvider((ref)=> name);
I want this, so that this string will be available all over the app.
However, providers have to been defined top level, so I'm not sure how to get the data there?
Meaning, in the above http request I make, in the .then function which is called on the result of the request, I want to store there the value into a provider. How to I create a provider there? Since the provider is global, I don't know how to save the result data String into the provider
I hope the question is clear, and thanks for the help!
To read a provider, you need a WidgetRef. You can pass it on getPreloadList . In this case it will be
final nameProvider = StateProvider.autoDispose((ref) => "");
class PreLoadApi {
getPreloadList(WidgetRef ref) {
//Future.delayed will be your http.get
Future.delayed(Duration(seconds: 3)).then((value) {
ref.read(nameProvider.notifier).state = "new Value";
});
}
}
To have a widgetRef you can wrap the widget with Consumer
return Consumer(
builder: (context, ref, child) => Scaffold(
floatingActionButton: FloatingActionButton(
onPressed: () {
PreLoadApi api = PreLoadApi();
api.getPreloadList(ref);
},
),
body: Text(ref.watch(nameProvider)),
There are others way handling this like getting text from future instead of passing WidgetRef. Also check StateNotifierProvider, ChangeNotifierProvider.
You can start from riverpod.dev
Because your "name" is valid only after a Future completes, the most likely holder for the value is a FutureProvider. Nicely, this will cache the value, as long as you don't make the provider autoDispose.
I am trying to get Contact using the function getContactsForPhone
getName()async{
number = '123-456-7890'
return await ContactsService.getContactsForPhone(number).then((value) => value.elementAt(0).displayName.toString());
}
but I am getting Future<dynmaic> instead of .displayName which is supposed to be String
You are mixing it up two way's to use Futures:
You can use await keyword to await for the conclusion.
You can use the then method to have a callback when the Future ends.
You need to choose one and stick with it. Using the await is always preferable because it makes the code more readable and avoids some callback hells.
In your case:
Future<String> getName() async {
number = '123-456-7890'
Iterable<Contact> myIterable = await ContactsService.getContactsForPhone(number);
List<Contact> myList = myIterable.toList();
return myList[0].displayName.toString()
}
Which should return the DisplayName you wanted.
Remember to also use the await keyword from the outside, wherever you call this function.
You can read more about Future and Asynchronous code here.
I use api for get information which need to be display
Future <String> Get_Amount_Jackpot() async {
// SERVER LOGIN API URL
var url2 = 'https://www.easytrafic.fr/game_app/get_jackpot_lotto.php';
// Starting Web API Call.
var response2 = await http.get(url2,headers: {'content-type': 'application/json','accept': 'application/json','authorization': globals.token});
// Getting Server response into variable.
Map<String, dynamic> jsondata2 = json.decode(response2.body);
return jsondata2["value"];
}
I call it here :
void initState() {
ListLotto = Grille_display();
jackpot = Get_Amount_Jackpot();
super.initState();;
}
How i can display the value "jackpot" which is a simple number on mobile screen. Note i use futurebuilder for another api request, this is why it is complicated. Normally i use futurebuilder for display async data but there i need 2 différents api request so 2 futureBuilder ??? Is it possible and how do that ?
You can use then to get the returned value from the function.
Get_Amount_Jackpot().then((value){
//value is what is returned from the function
jackpot = value;
});
I'm not sure if you can use uppercase letter as the start of a function name, but i copied your function name for my answer. Hope this helps.
I'm new to flutter. Basically I'm using code Igniter framework for my web application. I created REST API for my web app, after user login using API all the methods check for the session_id if it exists then it proceeds, and if it doesn't then it gives
{ ['status'] = false, ['message'] = 'unauthorized access' }
I'm creating app with flutter, when i use the http method of flutter it changes session on each request. I mean, it doesn't maintain the session. I think it destroys and creates new connection each time. Here is thr class method which i use for api calls get and post request.
class ApiCall {
static Map data;
static List keys;
static Future<Map> getData(url) async {
http.Response response = await http.get(url);
Map body = JSON.decode(response.body);
data = body;
return body;
}
static Future postData(url, data) async {
Map result;
http.Response response = await http.post(url, body: data).then((response) {
result = JSON.decode(response.body);
}).catchError((error) => print(error.toString()));
data = result;
keys = result.keys.toList();
return result;
}
I want to make API request and then store session_id,
And is it possible to maintain session on the server so i can manage authentication on the web app it self.?
HTTP is a stateless protocol, so servers need some way to identify clients on the second, third and subsequent requests they make to the server. In your case you might authenticate using the first request, so you want the server to remember you on subsequent requests, so that it knows you are already authenticated. A common way to do this is with cookies.
Igniter sends a cookie with the session id. You need to gather this from each response and send it back in the next request. (Servers sometimes change the session id (to reduce things like clickjacking that we don't need to consider yet), so you need to keep extracting the cookie from every response.)
The cookie arrives as an HTTP response header called set-cookie (there may be more than one, though hopefully not for simplicity). To send the cookie back you add a HTTP request header to your subsequent requests called cookie, copying across some of the information you extracted from the set-cookie header.
Hopefully, Igniter only sends one set-cookie header, but for debugging purposes you may find it useful to print them all by using response.headers.forEach((a, b) => print('$a: $b'));. You should find Set-Cookie: somename=abcdef; optional stuff. We need to extract the string up to, but excluding the ;, i.e. somename=abcdef
On the next, and subsequent requests, add a request header to your next request of {'Cookie': 'somename=abcdef'}, by changing your post command to:
http.post(url, body: data, headers:{'Cookie': cookie})
Incidentally, I think you have a mismatch of awaits and thens in your code above. Generally, you don't want statics in classes, if they should be top level functions instead. Instead you could create a cookie aware class like:
class Session {
Map<String, String> headers = {};
Future<Map> get(String url) async {
http.Response response = await http.get(url, headers: headers);
updateCookie(response);
return json.decode(response.body);
}
Future<Map> post(String url, dynamic data) async {
http.Response response = await http.post(url, body: data, headers: headers);
updateCookie(response);
return json.decode(response.body);
}
void updateCookie(http.Response response) {
String rawCookie = response.headers['set-cookie'];
if (rawCookie != null) {
int index = rawCookie.indexOf(';');
headers['cookie'] =
(index == -1) ? rawCookie : rawCookie.substring(0, index);
}
}
}