Question

我在初始状态下定义了一个对象，但是当我尝试检查状态是否为空时，这是我的AppState：

@immutable
class AppState {
  final bool isLoading;
  final int bottomNavIndex;
  final Poscomp poscomp;

  AppState({this.isLoading = false, this.poscomp, this.bottomNavIndex});

  factory AppState.loading() => AppState(
        isLoading: true,
        poscomp: Poscomp(exams: []),
        bottomNavIndex: 0,
      );

  AppState copyWith({
    bool isLoading,
    Poscomp poscomp,
    int bottomNavIndex,
  }) {
    return AppState(
      isLoading: isLoading ?? this.isLoading,
      poscomp: poscomp ?? this.poscomp,
      bottomNavIndex: bottomNavIndex ?? this.bottomNavIndex,
    );
  }
}

Poscomp的定义：

@immutable
class Poscomp {
  final List<Exam> exams;

  Poscomp({this.exams = const []});

  Poscomp copyWith({List<Exam> exams}) {
    return Poscomp(
      exams: exams ?? this.exams,
    );
  }

  @override
  int get hashCode => exams.hashCode;

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is Poscomp &&
          runtimeType == other.runtimeType &&
          exams == other.exams;

  @override
  String toString() {
    return 'Poscomp{exams: $exams}';
  }
}

当我尝试访问状态的其他属性时，它可以正常工作，但是对象始终返回null。

Answer 1

显然，当我们调度一个动作时，其他没有reducer的属性都被重新定义为null，那么我需要做的是：

为该对象定义一个化简器：

import 'package:computeiro/store/models/index.dart';
import 'package:computeiro/store/reducers/index.dart';

AppState appReducer(AppState state, action) {
  return AppState(
    isLoading: loadingReducer(state.isLoading, action),
    poscomp: poscompReducer(state.poscomp, action), //HERE
    bottomNavIndex: bottomNavReducer(state.bottomNavIndex, action),
  );
}

为Poscomp定义一个新的构造函数：

factory Poscomp.init() => new Poscomp(
      exams: [Exam(question: 'What is somethine?', answer: Answer.A)]);

并在AppState中调用它：

factory AppState.initial() => new AppState(
        isLoading: true,
        poscomp: Poscomp.init(),
        bottomNavIndex: 1,
      );

如何在Redux Flutter应用程序状态下定义对象并访问属性？

1 个答案: