Flutter 更新 Riverpod 保存数据的当前状态

Question

就像这个示例代码一样，它包含在Riverpod示例代码中，用于更新存储数据的当前状态：

state = [
  for (final todo in state)
    if (todo.id == id)
      Todo(
        id: todo.id,
        completed: todo.completed,
        description: description,
      )
    else
      todo,
];

我尝试在我的班级数据上实现它，但它将数据保存为新数据而不更新选定状态，我的班级数据：

class OrderStructure {
  final String title;
  final List<SelectedProducts> products;

  const OrderStructure(this.title, this.products);
}

class SelectedProducts {
  final int id;
  final List<SelectedProductServices> services;

  SelectedProducts(this.id, this.services);
}

class SelectedProductServices {
  final int id;
  final int count;
  final int cost;

  const SelectedProductServices(this.id, this.count, this.cost);
}

在这里，我尝试找到产品的服务并将其更新为递减count-1 ，但在搜索我的代码后，将新服务添加到产品中并且无法更新

void decrement(int productId, int serviceId) {
  final newState = OrderStructure(state.title, [
    ...state.products,
    for (final product in state.products)
      if (product.id == productId)
        for (final service in product.services)
          if (service.id == serviceId)
            SelectedProducts(productId, [
              ...product.services.where((s) => s.id == serviceId),
              SelectedProductServices(service.id, service.count - 1, service.cost)
            ])
          else
            SelectedProducts(productId,product.services)
  ]);

Answer 1

听起来您需要实现StateNotifier子类。 这只是一个草图，我还没有尝试过：

class OrderStructureState extends StateNotifier<OrderStructure> {
  // TODO: Add constructor with default value    

  void decrement(int productId, int serviceId) {
    state = OrderStructure(state.title, [
...state.products,
for (final product in state.products)
  if (product.id == productId)
    for (final service in product.services)
      if (service.id == serviceId)
        SelectedProducts(productId, [
          ...product.services.where((s) => s.id == serviceId),
          SelectedProductServices(service.id, service.count - 1, service.cost)
        ])
      else
        SelectedProducts(productId,product.services)

]); } }

请务必阅读文档。 这也可能有帮助：

https://codewithandrea.com/videos/flutter-state-management-riverpod/#statenotifierprovider