CODEWITHSUNDEEP
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Fahmi Sawalha
Fahmi Sawalha

Reputation: 622

dart : handle api failures with the use of either

i don't know what i am doing wrong or how to do it probably , in firebase it has been much easier with the FirebaseAuthException but here in a normal api i dont know how to handle my failures , like when it is 404 i want to display a specific error but i have reached a dead end because the IDE always tells me that The body might complete normally, causing 'null' to be returned, but the return type is a potentially non-nullable type. Try adding either a return or a throw statement at the end. iam returning a failure ate the end so what's the problem ? and i want to handle every failure not only socketexception . thank you !

import 'dart:convert';
import 'dart:io';
import 'package:dartz/dartz.dart';
import 'package:mscmu/domain/i_api_request/failures/api.failures.dart';
import '../../../../domain/i_api_request/folders/contracts/i.folders.repository.dart';
import '../../../../domain/models/foldermodel.dart';
import 'package:http/http.dart' as http;

class FolderRepository implements IFolderRepository {
  @override
  Future<Either<ApiFailures, List<FolderModel>>> mainFolders(int courseId) async {
    final response = await http.post(
      Uri.parse("http://xxxxxxxxxxxxxxx.php"),
      body: {"flag": "selectmainfolders", "course": "$courseId"}
    );
    try {
      if (response.statusCode == 200) {
        var l = json.decode(response.body) as List<dynamic>;
        var folders = l.map((e) => FolderModel.fromJson(e)).toList();
        return right(folders);
      } 
    } on SocketException catch(error) {
      return left(ApiFailures.badRequest());
    }
  }
}

Upvotes: 0

Views: 700

Answers (2)

Thierry
Thierry

Reputation: 8383

You are missing an else statement:

class FolderRepository implements IFolderRepository {
  @override
  Future<Either<ApiFailures, List<FolderModel>>> mainFolders(int courseId) async {
    final response = await http.post(
      Uri.parse("http://xxxxxxxxxxxxxxx.php"),
      body: {"flag": "selectmainfolders", "course": "$courseId"}
    );
    try {
      if (response.statusCode == 200) {
        [...]
        return right(folders);
      } else { // 404, 500, ...
        [...]
        return ???;
      }
    } on SocketException catch(error) {
      return left(ApiFailures.badRequest());
    }
  }
}

If you use just a

if ([...]) {
  [...]
  return something;
}

or a

if ([...]) {
  [...]
  return something;
}
else if ([...]) {
  [...]
  return somethingElse;
}

Then, you are missing the else branch that will return null and cause your error.

Upvotes: 1

Ardeshir ojan
Ardeshir ojan

Reputation: 2419

Your function must return something that socketexception wont work on every error ... you should add return something when the response.statusCode is not 200

if (response.statusCode == 200) {
      var l = json.decode(response.body) as List<dynamic>;
      var folders = l.map((e) => FolderModel.fromJson(e)).toList();
      return right(folders);
}else{
   ////////return something
}

you got to return Either<ApiFailures, List<FolderModel>> as you have written in your function

Upvotes: 0

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