Mobx 状态树引用类型和 Typescript

Question

我在 React 应用程序中使用带有 Typescript 的 mobx-state-tree。而且，我遇到了 Typescript 的问题，它抱怨 mobx 类型 types.safeReference 的类型。看起来模型定义中 safeReference 的类型与您使用 .create() 实际创建模型实例时的类型不同。在我的代码中，selectedProduct 的类型在 productStore 中转换为 string | number | undefined | null，但在模型定义中是 IStateTreeNode<...> | undefined | null，这就是我在根存储中出错的原因。我该如何解决？

这是我的产品商店：

import { types } from "mobx-state-tree";

const Product = types.model("Product", {
   id: types.identifier,
   name: types.string
})

const ProductStore = types
  .model("ProductStore", {
    products: types.array(Product),
    selectedProduct: types.safeReference(Product),
  })
  .actions((self) => ({
      // actions here
  }));

export const productStore = ProductStore.create({
  products: [],
  selectedProduct: undefined // the type here is different from the type in the actual model
});

而且，这是我的根存储区：

import { types } from "mobx-state-tree";
import ProductStore, { productStore } from "./product-store";

const RootStore = types.model('RootStore', {    
  productStore: ProductStore 
})

export const rootStore = RootStore.create({
    productStore: productStore // Here is where I get the typescript error.
});

更新：

重现此问题的另一种方法是尝试创建自定义引用。 getter 会抱怨 undefined 无法分配给类型 {...}。

const ProductByIdReference = types.maybeNull(
  types.reference(Product, {
      get(id: number, parent: Instance<typeof ProductStore>) {
          return parent.products.find(p => p.id === id) || undefined
      },
      set(value: Instance<typeof Product>) {
          return value.id
      }
  })
)

Answer 1

我详细检查了你的问题并写了一个解决方案，这是如何正确使用 mst rootStore 概念，不需要创建你的商店或对象的实例，只是 @inject 它直接在组件内部：

// Product Store
import { types, Instance } from "mobx-state-tree";

const Product = types.model("Product", {
  id: types.identifier,
  name: types.string
})

const Store = types
  .model("ProductStore", {
    products: types.array(Product),
    selectedProduct: types.safeReference(Product),
  })
  .actions((self) => ({
    // actions here
  }));

type ProductStoreType = typeof Store;
interface ProductStoreTypeInterface extends ProductStoreType {}
export interface ProductStoreInterface extends Instance<ProductStoreTypeInterface> {}
export const ProductStore: ProductStoreTypeInterface = Store;

// Root Store
import { types } from "mobx-state-tree";
import { ProductStore } from "./product-store";

const RootStore = types.model('RootStore', {
  productStore: types.late(() => types.optional(ProductStore, {})),
})

// And now you can create rootStore with empty object
export const rootStore = RootStore.create({});

// Component
import { inject, observer } from 'mobx-react';
import { SettingStoreInterface } from "../settings/SettingStore";
import React from "react";

interface ComponentProps {}

interface InjectedProps extends ComponentProps {
  productStore: ProductStoreInterface;
}

@inject('productStore')
@observer
class SomeComponent extends React.Component<ComponentProps> {
  componentDidMount() {
    const { productStore } = this.props as InjectedProps;
    
    console.log(productStore.products);
  }
}

Answer 2

一般来说，当您尝试在通常使用实例的地方使用快照时，您会使用 cast. When you are trying to use an instance where a snapshot is typically used, you use castToSnapshot。

export const rootStore = RootStore.create({
    productStore: castToSnapshot(productStore)
});

Mobx 状态树引用类型和 Typescript

Mobx State Tree reference type and Typescript

typescript

reactjs

mobx

mobx-react

mobx-state-tree