React useState 钩子不更新状态

Question

我遇到了 useState 问题。下面是codesandbox

中的代码运行ning

这是代码本身；

import React, { Fragment, useState } from "react";
import ReactDOM from "react-dom";

type FormElem = React.FormEvent<HTMLFormElement>;

interface ITodo {
  text: string;
  complete: boolean;
}

export default function App(): JSX.Element {
  const [value, setValue] = useState<string>("");
  const [todos, setTodos] = useState<ITodo[]>([]);

  const handleSubmit = (e: FormElem): void => {
    e.preventDefault();
    addTodo(value);
    setValue("");
  };

  const addTodo = (text: string): void => {
    const newTodos: ITodo[] = [...todos, { text, complete: false }];
    setTodos(newTodos);
  };

  const completeTodo = (index: number): void => {
    const newTodos: ITodo[] = todos;
    newTodos[index].complete = !newTodos[index].complete;
    setTodos(newTodos);
  };

  return (
    <Fragment>
      <h1>Todo List</h1>
      <form onSubmit={handleSubmit}>
        <input
          type="text"
          value={value}
          onChange={e => setValue(e.target.value)}
          required
        />
        <button type="submit">Add Todo</button>
      </form>
      <section>
        {todos.map((todo: ITodo, index: number) => (
          <Fragment key={index}>
            <div>{todo.text}</div>
            <button type="button" onClick={() => completeTodo(index)}>
              {" "}
              {todo.complete ? "Incomplete" : "Complete"}{" "}
            </button>
          </Fragment>
        ))}
      </section>
    </Fragment>
  );
}

const root = document.getElementById("root");

ReactDOM.render(<App />, root);

单击完成按钮时，它只会运行一次 completeTodo 函数，并且不会再次运行即使 setTodos 函数是运行并且待办事项已更新。

这曾经在 react 16.7.0-alpha-2 中有效，但现在版本 16.8.1 似乎无法更新。

如果您有任何建议，请告诉我，这里再次显示代码运行ning in codesandbox;

https://codesandbox.io/s/kmznl0345r

Answer 1

您目前正在改变 completeTodo 函数中的 todo 对象。如果您改为使用 todos 中的所有元素创建一个新数组，并在 complete 切换的位置创建一个新对象，它将按预期工作。

const completeTodo = (index: number): void => {
  const newTodos: ITodo[] = [...todos];
  newTodos[index] = {
    ...newTodos[index],
    complete: !newTodos[index].complete
  };
  setTodos(newTodos);
};

React useState 钩子不更新状态

React useState hook isn't updating the state

javascript

reactjs

react-hooks