Dynamic Generation of Form Fields Based on Database Values

main.dart

// Assumption is, all the fields hold the same kind of value
// An entry from the database together with the ID
class Measurement {
  final int id;
  final String name;
  Measurement({this.id, this.name});
}

// Field Instance class defines the variables that will be used for each field
class FieldInstance {
  // Controller to manage how text is edited
  final TextEditingController controller;
  
  final BehaviorSubject<String> subject;
  // Measurement a class instance that holds one entry from the
  //database and it's ID
  final Measurement measurement;
  final Function(String) onChanged;
  final Stream<String> value;

  FieldInstance({
    this.controller,
    this.subject,
    this.measurement,
    this.onChanged,
    this.value,
  });
}

// Assuming you have fetched your list from the database and 
// formatted it to sth fancy
var measurements = [Measurement(id: 21, name: "Hips"),
                    Measurement(id: 1, name: "Neck"),
                    Measurement(id: 2, name: "Shoulders")
                   ];

final _subject = BehaviorSubject<String>();
// Loop through the measurements, in your case engines 
// and create an array of field instances
final fields = measurements.map((measurement) => FieldInstance(
  controller: TextEditingController(),
  subject: _subject,
  measurement: measurement,
  onChanged: _subject.sink.add,
  value: _subject.stream,
)).toList();

// Finally in the Widget, loop through the fields and create the form

...
  Column(children: [
    // Generate a list of widgets for the column and spread (...) them
    ...fields.map((field) => TextFormField(
      controller: field.controller,
      onChanged: field.onChanged,
      decoration: InputDecoration(
                    labelText: field.measurement.name,
                    labelStyle: TextStyle(
                      color: formLabel,
                    ),
                    errorText: snapshot.error,
                  ),
    )).toList(),
  ]),