即使超时,同一处理程序中的useState更新状态也不可用 [英] useState updated state not available in the same handler even with timeout
本文介绍了即使超时,同一处理程序中的useState更新状态也不可用的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个包含3个字段的简单注册表。我已经将状态存储在formValues中,其中value
&;error
与每个字段相关联。现在,当我在没有填写任何或至少一个字段的情况下提交表单时,表单应该是无效的,但是它会显示包含无效字段的验证消息,但使表单有效。即使我添加了setTimeout
,更新后的状态在相同的handleSubmit
中也不可用。如果我再次提交,该过程运行良好。我知道状态更新是异步的,但是如果我们在控制台中看到日志,则在formValues
渲染日志之后记录表单的验证消息,这些日志显示状态已正确更新,但最终的验证消息显示无效状态。如果我将其更改为class component,它就可以工作。这里有一个linkto codesandbox。
import React, { useState } from "react";
import { Button, Form, Col } from "react-bootstrap";
const sleep = timeout => new Promise(resolve => setTimeout(resolve, timeout));
const RegistrationForm = () => {
const [formValues, setFormValues] = useState({
name: { value: "", error: null },
email: { value: "", error: null },
password: { value: "", error: null }
});
const handleInputChange = (e, field) => {
const { value } = e.target;
setFormValues(prevValues => ({
...prevValues,
[field]: { value, error: null }
}));
};
const validateForm = () => {
let updatedFormValues = { ...formValues };
Object.keys(formValues).forEach(field => {
if (!formValues[field].value) {
updatedFormValues = {
...updatedFormValues,
[field]: { ...updatedFormValues[field], error: "required" }
};
}
});
setFormValues(updatedFormValues);
};
const isFormValid = () =>
Object.keys(formValues).every(field => formValues[field].error === null);
const handleSubmit = async e => {
e.preventDefault();
validateForm();
await sleep(100);
if (!isFormValid()) {
console.log("form is not valid", formValues);
return;
}
console.log("form is valid", formValues);
// make api call to complete registration
};
console.log({ formValues });
return (
<Form className="registration-form" onSubmit={handleSubmit}>
<Form.Row>
<Col>
<Form.Group controlId="name">
<Form.Label>Name</Form.Label>
<Form.Control
type="text"
placeholder="Enter name"
value={formValues.name.value}
onChange={e => handleInputChange(e, "name")}
/>
<Form.Control.Feedback type="invalid" className="d-block">
{formValues.name.error}
</Form.Control.Feedback>
</Form.Group>
</Col>
<Col>
<Form.Group controlId="email">
<Form.Label>Email</Form.Label>
<Form.Control
type="email"
placeholder="Enter email"
value={formValues.email.value}
onChange={e => handleInputChange(e, "email")}
/>
<Form.Control.Feedback type="invalid" className="d-block">
{formValues.email.error}
</Form.Control.Feedback>
</Form.Group>
</Col>
</Form.Row>
<Form.Row>
<Col>
<Form.Group controlId="password">
<Form.Label>Password</Form.Label>
<Form.Control
type="password"
placeholder="Enter password"
value={formValues.password.value}
onChange={e => handleInputChange(e, "password")}
/>
<Form.Control.Feedback type="invalid" className="d-block">
{formValues.password.error}
</Form.Control.Feedback>
</Form.Group>
</Col>
<Col />
</Form.Row>
<Button variant="primary" type="submit">
Submit
</Button>
</Form>
);
};
export default RegistrationForm;
推荐答案
状态更新不仅是异步的,而且还会受到功能组件中的关闭的影响,因此使用休眠或超时不会在同一呈现周期内为您留下更新值
您可以在此帖子中了解更多信息:
useState set method not reflecting change immediately
但是,在您的案例中,一种解决方案是维护ref并切换is值以触发useEffect,您将在其中验证表单POST句柄Submit处理程序验证它并设置formValues
相关编码:
const validateFormField = useRef(false);
const handleInputChange = (e, field) => {
const { value } = e.target;
setFormValues(prevValues => ({
...prevValues,
[field]: { value, error: null }
}));
};
const validateForm = () => {
let updatedFormValues = { ...formValues };
Object.keys(formValues).forEach(field => {
if (!formValues[field].value) {
updatedFormValues = {
...updatedFormValues,
[field]: { ...updatedFormValues[field], error: "required" }
};
}
});
setFormValues(updatedFormValues);
validateFormField.current = !validateFormField.current;
};
const isFormValid = () =>
Object.keys(formValues).every(field => formValues[field].error === null);
const handleSubmit = async e => {
e.preventDefault();
validateForm();
// make api call to complete registratin
};
useEffect(() => {
if (!isFormValid()) {
console.log("form is not valid", formValues);
} else {
console.log("form is valid", formValues);
}
}, [validateFormField.current]); // This is fine since we know setFormValues will trigger a re-render
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