Initializing an input in a form for submission - flutter

Question

I am trying to send an API post through my flutter app:
The user inserts the log_weight through a textfield which inside table inside a Form. The row of the table are iterations from a list.
In my flutter app I have created a table that iterates through a list inside a form. So I am trying to get a log submission from each iteration.
Here is my api_serice.dart:
class APIService {
static var client = http.Client();
Future<http.Response> addLog(
int logWeight) async {
var url = Uri.parse(Config.apiURL +
Config.userAddlogAPI);
final response = await http.post(url, headers: {
HttpHeaders.authorizationHeader:
'Token xxxxxxxxxxxxxxxxxx',
}, body: {
'log_weight': logWeight,
});
}
Here is the exercises.dart:
class Exercises extends StatefulWidget {
#override
_ExercisesState createState() => _ExercisesState();
}
class _ExercisesState extends State<Exercises> {
late Map<String, int> arguments;
late int logWeight;
Here is the form:
Builder(builder: (context) {
return Form(
key: key,
child: Table(
children: [
const TableRow(children: [
Text(
'',
style: TextStyle(
fontSize: 15,
fontWeight:
FontWeight.bold,
color: Colors.black,
),
),
Text(
'Weight',
style: TextStyle(
fontSize: 15,
fontWeight:
FontWeight.bold,
color: Colors.black,
),
),
Text(
'New Weight',
style: TextStyle(
fontSize: 15,
fontWeight:
FontWeight.bold,
color: Colors.black,
),
),
Text(
'Submit',
style: TextStyle(
fontSize: 15,
fontWeight:
FontWeight.bold,
color: Colors.black,
),
)
]),
// Iterate over the breakdowns list and display the sequence information
for (var breakdown in snapshot
.data![index].breakdowns)
TableRow(children: [
Text(
'${breakdown.order}',
style: const TextStyle(
fontSize: 15,
color: Colors.black,
),
),
Text(
'${breakdown.weight}',
style: const TextStyle(
fontSize: 15,
color: Colors.black,
),
),
TextFormField(
decoration:
InputDecoration(
border:
InputBorder.none,
),
style: const TextStyle(
fontSize: 15,
color: Colors.black,
),
validator: (value) {
if (value == null) {
return 'Please enter a valid number';
}
return null;
},
onSaved: (value) {
logWeight =
int.parse(value!);
},
),
OutlinedButton(
onPressed: () async {
final Map<String, int>
arguments =
ModalRoute.of(
context)!
.settings
.arguments
as Map<String,
int>;
final int id =
arguments['id'] ??
0;
try {
if (Form.of(context)
?.validate() ==
true) {
Form.of(context)
?.save();
APIService.addLog(
id,
logWeight);
}
} catch (error) {
await showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: Text(
'Error'),
content: Text(error
.toString()),
actions: [
OutlinedButton(
child: Text(
'OK'),
onPressed:
() {
Navigator.of(
context)
.pop();
}, ),],);},);}},
child: Text('Submit'),
),]),],),);
How can I fix my code so that I can send the log_weight. I keep getting E/flutter ( 4353): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: LateInitializationError: Field 'logWeight' has not been initialized.

Answer 1

The error is caused by late keyword. variables that are late must be initialized. Try not to use late that much.
Solution 1. make logWeight non-nullable and initialize it. Because your addLog method only allows non-nullable logWeight value.
int logWeight = 0;
Solution 2. make logWeight nullable and before calling the api, check if it's null or not. (If logWeight is required param for your api)
int? logWeight;
---
if(logWeight != null) {
APIService.addLog(id,logWeight);
}
or use validation
Solution 3. (If logWeight is not required param for your api) just make logWeight nullable and change your method to allow nullable logWeight value
int? logWeight;
---
class APIService {
static var client = http.Client();
Future<http.Response> addLog(
int? logWeight) async {
...
}