آموزش کار با پکیج Freezed در فلاتر

class FreezedExamplePage extends StatefulWidget {
  @override
  _FreezedExamplePageState createState() => _FreezedExamplePageState();
}

class _FreezedExamplePageState extends State<FreezedExamplePage> {
  Random _random;
  Product _product;

  @override
  void initState() {
    super.initState();
    _product = Product(id: "1", name: "iPhone 12");
    _random = Random();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Immutability and Equality"),
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.refresh),
        onPressed: _randomProductData,
      ),
      body: ListTile(
        leading: CircleAvatar(
          backgroundColor: _product.color,
        ),
        title: Text(
          _product.name,
        ),
        subtitle: Text(
          _product.id,
        ),
      ),
    );
  }

  void _randomProductData() {
    final randomNumber = _random.nextInt(12);
    setState(
      () => _product = _product.copyWith(
        name: "iPhone $randomNumber",
      ),
    );
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      debugShowCheckedModeBanner: false,
      home: FreezedExamplePage(),
    );
  }
}

dependencies:
  flutter:
    sdk: flutter

  freezed_annotation: ^0.12.0

dev_dependencies:
  flutter_test:
    sdk: flutter

  build_runner:
  freezed: ^0.12.2

import 'package:flutter/material.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

part 'product.freezed.dart';

@freezed
abstract class Product with _$Product {
  const factory Product({
    String id,
    String name,
    Color color,
  }) = _Product;
}

flutter pub run build_runner build

_product = Product(id: "1", name: "iPhone 12");

final _newProduct = _product.copyWith(
  name: "My new name",
);

@freezed
abstract class Product with _$Product {
  const factory Product({
    String id,
    String name,
    @Default(Colors.red) Color color,
  }) = _Product;
}

@freezed
abstract class Product with _$Product {
  const factory Product({
    required String id,
    required String name,
    @Default(Colors.red) Color color,
  }) = _Product;
}

@freezed
abstract class Product with _$Product {
  @Assert("name != 'iPhone 13', 'iPhone 13 has yet to be released!'")
  const factory Product({
    required String id,
    required String name,
    @Default(Colors.red) Color color,
  }) = _Product;
}

@freezed
abstract class Product with _$Product {
  const Product._();

  @Assert("name != 'iPhone 13', 'iPhone 13 has yet to be released!'")
  const factory Product.phone({
    required String id,
    required String name,
    @Default(Colors.red) Color color,
  }) = _Phone;

  const factory Product.insurance({
    required String id,
    required String name,
    required double quote,
  }) = _Insurance;

  @override
  String toString() {
    return "Product ID = $id, Name = $name";
  }
}

class _FreezedExamplePageState extends State<FreezedExamplePage> {
  List<Product> _productList;

  @override
  void initState() {
    super.initState();

    _productList = [
      Product.phone(id: "1", name: "iPhone 12"),
      Product.insurance(id: "2", name: "Home Insurance", quote: 25.44)
    ];

    _productList.forEach((Product product) {
      product.map(
          phone: (Product phone) => print("Phone!"),
          insurance: (Product insurance) =>
              print("Insurance!"));
    });
  }

  //
}

flutter: Phone!
flutter: Insurance!

import 'package:freezed_annotation/freezed_annotation.dart';

part 'ui_state.freezed.dart';

@freezed
abstract class UIState with _$UIState {
  const factory UIState.initial() = Initial;
  const factory UIState.loading() = Loading;
  const factory UIState.success() = Success;
  const factory UIState.error(Failure failure) = Error;
}

class _FreezedExamplePageState extends State<FreezedExamplePage> {
  UIState _uiState;

  @override
  void initState() {
    super.initState();
    _uiState = Initial();
  
  }

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: const Text("Immutability and Equality"),
    ),
    body: _uiState.when(
      initial: _buildProductsLoading,
      loading: _buildProductsLoading,
      success: _buildProductsSuccess,
      error: _buildProductsError,
    ),
  );
}

}