form_data

form_data.dart

import 'package:flutter/widgets.dart';

class FormData<FormDataType> {
  FormDataType data;
  final List<FormEntry> _fields = <FormEntry>[];

  FormData({@required this.data});

  FormEntry add<FieldType>(
    FieldType value, {
    FormDataType Function(FieldType value) onSaved,
    String Function(FieldType value) validator,
    FocusNode focusNode,
  }) {
    final field = FormEntry(
      initialValue: value,
      onSaved: (v) {
        if (onSaved != null) data = onSaved(v);
      },
      validator: validator,
    );
    _fields.add(field);
    return field;
  }

  void nextEmpty() {
    final fieldNode = _fields.firstWhere((field) => !field.filled, orElse: () => null)?.focusNode;
    if (fieldNode == null) {
      unfocusAll();
      //_buttonFocusNode.requestFocus();
    } else {
      fieldNode.requestFocus();
    }
  }

  void valid() => _fields.every((field) => field.validator(field.value) == null);

  void unfocusAll() => _fields.map<FocusNode>((field) => field.focusNode).forEach((node) => node.unfocus());

  void setValidationStatus() => _fields.every((field) => field.filled);

  FormDataType submit(BuildContext context) {
    unfocusAll();
    final form = Form.of(context)..save();
    if (!form.validate()) {
      nextEmpty();
      return null;
    }
    return data;
  }

  void dispose() {
    for (final field in _fields) {
      field.dispose();
    }
  }
}

/// Form field proxy
@immutable
class FormEntry<FieldType> {
  final FieldType initialValue;

  FieldType get value => FieldType == String ? (_controller as TextEditingController).value.text : _controller.value;
  set value(FieldType newValue) => _controller.value = newValue;

  final FocusNode focusNode;

  /// Check if field filled
  bool get filled => !hasValidator || _onSaved == null || validator(value) == null;

  /// On Form saved
  ValueChanged<FieldType> get onSaved => _onSaved;
  final ValueChanged<FieldType> _onSaved;

  /// On field change
  ValueChanged<FieldType> get onChanged => (dynamic value) => _controller.value = value;

  /// Field validation
  FormFieldValidator<FieldType> get validator => (dynamic value) => hasValidator ? _validator(value) : null;
  final String Function(FieldType value) _validator;

  /// If validator set
  final bool hasValidator;

  final ValueNotifier _controller;
  ValueNotifier<T> controller<T>() => _controller as ValueNotifier<T>;

  void addListener(VoidCallback listener) => _controller.addListener(listener);
  void removeListener(VoidCallback listener) => _controller.removeListener(listener);

  void dispose() {
    _controller.dispose();
  }

  FormEntry({
    @required this.initialValue,
    @required ValueChanged<FieldType> onSaved,
    String Function(FieldType value) validator,
    FocusNode focusNode,
  })  : focusNode = focusNode ?? FocusNode(),
        _onSaved = onSaved,
        _validator = validator,
        hasValidator = validator != null,
        _controller = FieldType == String ? TextEditingController(text: initialValue as String) : ValueNotifier<FieldType>(initialValue);
}