Question

我正在听关于udemy的反应课。现在我到达了代码的这一点

import java.util.regex.Pattern;

class Example {
    public static void main (String[] args) throws java.lang.Exception {
        check("aaaa", true);
        check("a", true);
        check("", true);
        check("m", true);
        check("n", true);
        check("mn", false);
        check("q", false);
        check("nnnn", false);
    }
    private static void check(String text, boolean expect) {
        boolean result = Pattern.matches("a*|[mn]", text);
        System.out.println(
            (result ? "Match   " : "No match") +
            (result == expect ? " OK    " : " ERROR ") +
            ": " + text
        );
    }
}

在编译后遇到此错误消息，我不知道该怎么做或意味着什么

import React, { useState } from 'react';
import Person from  './Person/Person';
import './App.css';

const app = props => {
    const [personState, setPersonState] = useState({
        persons: [
            {name: "Fil", age: 30}
        ],

        other: "other"
    });

    const switchHandler = () => {
        setPersonState({
            persons: [
                {name: "Fil", age: 40}
            ]
        })
    };

    return (
        <div className="App">
            <h1>I'm a react developer</h1>
            <Person name={personState.persons[0].name} age={personState.persons[0].age}>I am a children</Person>
            <button onClick={switchHandler}>Switch Name</button>
        </div>
    );
}

export default app;

Answer 1

您的app必须是PascalCase App。是要使其成为一个组件。

将const app =重命名为const App =

在函数“ app”中调用React Hook“ useState”，该函数既不是React函数组件也不是自定义React

1 个答案: