UI 不会使用 React Hooks 和表单提交重新渲染状态更新 [英] UI not re-rendering on state update using React Hooks and form submission

问题描述

我正在尝试使用 React Hooks 和表单更新 UI.我有一个状态设置来监视表单上的值，当我单击提交时，我想将此值添加到一个数组(保持状态)并将其显示在 UI 上.我的问题是，当我提交值时，虽然它被添加到数组中(并且状态已更新)，但 UI 仅在我更改输入中的值时更新.

我的组件如下:

const PushToArrayUpdateState = () =>{const [array, setArray] = useState([]);const [formVal, setFormVal] = useState(``);const handleSubmit = 事件 =>{event.preventDefault();让 updateArray = 数组；updateArray.push(formVal);控制台日志(更新数组)；设置数组(更新数组)；};返回 (<div><form onSubmit={handleSubmit}><input type="text" name="arrayVal" onChange={e =>setFormVal(e.target.value)}/><input type="submit" value="Submit"/></表单><div>{array.map((val, index) => <p key={index}>{val}</p>)}

);};

你也可以看到这个 [not] 工作于:https://codesandbox.io/s/p3n327zn3q

有没有人对为什么 handleSubmit 函数中的 setArray 没有自动导致组件重新渲染有任何建议?

解决方案

代替

let updateArray = array;

试试这个:

const updateArray = [...array];

https://codesandbox.io/embed/qxk4k3zmzq

因为 JS 中的数组是引用值，所以当你尝试使用 = 复制它时，它只会复制对原始数组的引用.

I'm trying to update a UI using React Hooks and a form. I have a state set to monitor the value on the form and when I click submit, I want to add this value to an array (held in state) and display it on the UI. My problem is that when I submit the value, although it is added to the array (and state is updated), the UI only updates when I change the value in the input.

My Component is as follows:

const PushToArrayUpdateState = () => {

    const [array, setArray] = useState([]);
    const [formVal, setFormVal] = useState(``);

    const handleSubmit = event => {
        event.preventDefault();
        let updateArray = array;
        updateArray.push(formVal);
        console.log(updateArray);
        setArray(updateArray);
    };

    return (
        <div>
            <form onSubmit={handleSubmit}>
                <input type="text" name="arrayVal" onChange={e => setFormVal(e.target.value)} />
                <input type="submit" value="Submit" />
            </form>
            <div>
                {array.map((val, index) => <p key={index}>{val}</p>)}
            </div>
        </div>
    );
};

You can also see this [not] working at: https://codesandbox.io/s/p3n327zn3q

Has anyone got any suggestions as to why the setArray in the handleSubmit function is not automatically causing the component to re-render?

解决方案

Instead of

let updateArray = array;

Try this:

const updateArray = [...array];

https://codesandbox.io/embed/qxk4k3zmzq

Because arrays in JS are reference values, so when you try to copy it using the = it will only copy the reference to the original array.

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