How do you properly use data from a JSON response body from a POST? - flutter

Question

I need to use some data from a JSON response body in an if statement. How would I go about accessing this data from the file that calls the function that performs the POST? (Or other files) Any help is appreciated! Thanks!
This is the function that performs the POST.
Future<User> loginUser(String username, String password) async {
final http.Response response = await http.post(
'https://fakeapiofcourse.com/login',
headers: <String, String>{
'Content-Type': 'application/json; charset=UTF-8',
},
body: jsonEncode(<String, String>{
'username': username,
'password': password
}),
);
if (response.statusCode <400) {
return User.fromJson(json.decode(response.body));
} else {
throw Exception('Failed to login user');
}
}
This is where I'll need to use the data first. In the If statement, I'll be using a Bool from the response body.
onPressed: () async {
bool success = true;
try {
await loginUser(passwordController.text, nameController.text);
} on Exception {
success = false;
}
// print(nameController.text);
-> if(THIS IS WHERE I NEED TO CHECK THE BOOL FROM THE BODY) {
Navigator.push(
context,
PageRouteBuilder(
transitionDuration: Duration(seconds: 1),
transitionsBuilder: (BuildContext context,
Animation<double> animation,
Animation<double> secAnimation,
Widget child) {
animation = CurvedAnimation(
parent: animation,
curve: Curves.elasticInOut);
return ScaleTransition(
scale: animation,
child: child,
alignment: Alignment.center,
);
},
pageBuilder: (BuildContext context,
Animation<double> animation,
Animation<double> secAnimation) {
return Dashboard();
}));}
},

Answer 1

Try something like this.
dynamic loginUser(String username, String password) async {
final http.Response response = await http.post(
'https://fakeapiofcourse.com/login',
headers: <String, String>{
'Content-Type': 'application/json; charset=UTF-8',
},
body: jsonEncode(<String, String>{
'username': username,
'password': password
}),
);
if (response.statusCode < 400) {
return json.decode(response.body);
} else {
throw Exception('Failed to login user');
}
}
Get the response from the function, then use it.
onPressed: () {
bool success = true;
var response;
try {
response = loginUser(passwordController.text, nameController.text);
User currentUser = User.fromJson(response);
} on Exception {
success = false;
}
if(response['SOME_FIELD'] == 'SOME_VALUE'){
.....
}else{
....
}
}
If you don't want this, simply just add that field to your User model, so that you can access it.
Hope that suits your case!

Answer 2

You can get your user object in this way:
var User user = null
try{
user = await loginUser(passwordController.text, nameController.text);
}on Exception{
success = false;
}
if(user.loggedIn && user != null){
Navigator.push()
}

Answer 3

Wait, you are calling loginUser but are not assigning the result to anything.
So just change your code to do:
onPressed: () async {
User user;
try {
user = await loginUser(passwordController.text, nameController.text);
} on Exception {
if (user != null) {
// now you can access whatever field of user you want
}
else {
// handle exception or a null user from your loginUser callcases where the
}