英文:
Formik useField
问题
The input syntax you're asking about, which is <input {...field} {...props} />, involves spreading the properties of the field and props objects into the <input> element. This is a feature in JavaScript called "object spreading" or "object destructuring assignment."
In this context:
-
fieldlikely contains specific properties related to form field management, such as thenameandvalueof the input field. -
propsprobably contains additional properties that you want to pass to the<input>element, such asplaceholder,type, or any other valid HTML attributes.
By spreading both field and props into the <input> element, you're essentially merging all the properties from these objects into the <input> tag, allowing you to set attributes and values for the input field easily.
This syntax simplifies the code and makes it more concise because you don't need to manually specify each attribute separately. Instead, you can pass all relevant properties as part of the field and props objects.
If you have any further questions or need more clarification, feel free to ask.
英文:
I'm trying to understand the useFormik() function.
There is an example of the syntax below:
const MyTextField = ({ label, ...props }) => {
const [field, meta, helpers] = useField(props);
return (
<>
<label>
{label}
<input {...field} {...props} />
</label>
{meta.touched && meta.error ? (
<div className="error">{meta.error}</div>
) : null}
</>
);
};
What I do not understand is the input syntax, why can we spread fields and props into an input tag? Does anyone know the logic behind it?
<input {...field} {...props} />
All the answers are welcome, thank you in advance!
I have looked it up in StackOverflow and the official document, but I still do not understand it.
答案1
得分: 0
-
useField钩子返回一个包含三个值的数组。 -
FieldInputProps
-
FieldMetaProps
-
FieldHelperProps
输入标签需要其必要的处理程序和值，如value、onChange等，所有这些都包含在FieldInputProps对象中，你在代码中将其解构为field。
const [field, meta, helpers] = useField(props);
所以，field本质上是一个具有以下可能值的对象[1]
{
name: 'somename',
onBlur: () => {}
onChange: () => {}
value: 'somevalue',
}
使用展开语法，我们实际上只是将整个对象直接传递给input标签，而不是手动逐个传递，如下所示，
<input value={field.value} name={field.name} onChange={field.onChange} ... />
与使用展开运算符相比 [2]
<input {...field} />
你的props对象也是类似的情况。
参考链接：
- https://formik.org/docs/api/useField#fieldinputpropsvalue
- https://sentry.io/answers/react-spread-operator-three-dots/
英文:
So the useField hook returns an array with three values.
- FieldInputProps
- FieldMetaProps
- FieldHelperProps
An input tags needs its necessary handlers and values like, value, onChange, etc. All these are present in the FieldInputProps object which you are destructuring as field in your code.
const [field, meta, helpers] = useField(props);
So, field is essentially an object with these possible values [1]
{
name: 'somename',
onBlur: () => {}
onChange: () => {}
value: 'somevalue',
}
With the spread syntax we are essentially just passing all the object directly to the input tag instead of manually passing one by one like,
<input value={field.value} name={field.name} onChange={field.onChange} ... />
v/s
Using spread operator [2]
<input {...field} />
Similar is the case for your props object.
Reference:
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