Question

我是第一次学习 ts 的初学者。预先感谢您分享您的知识。我正在制作一个todolist。我用反应来完成它。但是现在我用 react 和 typescript 一起来完成代码。

在我看来，'reducer' 工作不正常。我该如何操作？如果你让我知道，我将不胜感激。这是带有表面错误的“App.tsx”代码。

import React, { useState } from "react";
import Add from "./Add";
import List from "./List";
import ToDo from "./ToDo";
import Title from "./Title";
import Progress from "./Progress";
import styled from "styled-components";

interface ITodo {
  toDos: string;
  completed: boolean;
}

function App() {
  const { toDos, completed } = useState<ITodo>(); ? Error part
  return (
    <Title>
      <Add />
      <Progress />
      <Lists>
        <List title={toDos.length !== 0 ? "To Dos" : ""}>
          {toDos.map((toDo: any) => (
            <ToDo key={toDo.id} id={toDo.id} text={toDo.text} isCompleted={false} />
          ))}
        </List>
        <List title={completed.length !== 0 ? "Completed" : ""}>
          {completed.map((toDo: any) => (
            <ToDo key={toDo.id} id={toDo.id} text
              {...toDo.text} isCompleted />
          ))}
        </List>
      </Lists>
    </Title>
  );
}

export default App;

这段代码是我认为有问题的'reducer.tsx'代码。

import { v4 as uuidv4 } from "uuid";
import { ADD, DEL, COMPLETE, UNCOMPLETE, EDIT } from "./actions";

export const initialState = {
  toDos: [],
  completed: [],
};

const reducer = ({ state, action }: any) => {
  switch (action) {
    case ADD:
      return {
        ...state,
        toDos: [...state.toDos, { text: action.payload, id: uuidv4() }],
      };
    case DEL:
      return {
        ...state,
        toDos: state.toDos.filter((toDo: { id: number; }) => toDo.id !== action.payload),
      };
    case COMPLETE:
      const target = state.toDos.find((toDo: { id: number; }) => toDo.id === action.payload);
      return {
        ...state,
        toDos: state.toDos.filter((toDo: { id: number; }) => toDo.id !== action.payload),
        completed: [...state.completed, { ...target }],
      };
    case UNCOMPLETE:
      const aTarget = state.completed.find(
        (toDo: { id: any; }) => toDo.id === action.payload
      );
      return {
        ...state,
        toDos: [...state.toDos, { ...aTarget }],
        completed: state.completed.filter(
          (complete: { id: number; }) => complete.id !== action.payload
        ),
      };
    case EDIT:
      const bTarget = state.toDos.find((toDo: { id: number; }) => toDo.id === action.id);
      const rest = state.toDos.filter((toDo: { id: number; }) => toDo.id !== action.id);
      return {
        ...state,
        toDos: rest.concat({ ...bTarget, text: action.payload }),
      };
    default:
      return;
  }
};

export default reducer;

此代码是“context.tsx”代码。

import React, { createContext, useReducer, useContext } from 'react';
import reducer, { initialState } from "./reducer";

export type Todo = {
  id: number;
  text: string;
  done: boolean;
};

export type TodosState = Todo[];

const ToDosContext = createContext<TodosState | any>(undefined);

const ToDosProvider = ({ children }: { children: React.ReactNode }) => {
  const [state, dispatch] = useReducer(reducer, initialState);
  return (
    <ToDosContext.Provider value={{ state, dispatch }}>
      {children}
    </ToDosContext.Provider>
  );
};

export const useDispatch = () => {
  const { dispatch } = useContext(ToDosContext);
  return dispatch;
};

export const useState = () => {
  const { state } = useContext(ToDosContext);
  return state;
};

export default ToDosProvider;

Answer 1

这里发生的事情是由于命名混乱。您创建了一个自定义钩子 useState，它与一个内置的 React 钩子同名，但您使用了错误的钩子。

这里出现错误：

const { toDos, completed } = useState<ITodo>(); ? Error part

因此：

import React, { useState } from "react";

您想使用自定义 useState 钩子，它返回一个具有 toDos 和 completed 属性的对象。但是，您没有导入该钩子，而是导入了内置的 React 钩子 useState，它返回一个包含两个条目（state 和 setState）的数组。

进入 context.tsx 并将您的自定义挂钩重命名为不那么模糊的名称，例如 useTodosState 和 useTodosDispatch。这不是严格要求的，但它会让生活变得更轻松！

然后进入 App.tsx 并将 useState 替换为 useTodosState，确保从 context.tsx 导入它。既然您已经确定要使用哪个钩子，您就无需担心 IDE 会自动从 React 导入 useState。

类型 TS2339 上不存在属性“toDos”

1 个答案: