javascript - useState() 钩子(Hook)在设置新值时从对象中删除字段

Question

无法理解我在这里做错了什么。我有一个非常简单的对象状态:

const [itemInput, setItemInput] = useState({
    userId: userId,
    objectId: id,
    title: "",
    description: "",
    createdAt: new Date().getTime().toString(),
  })

然后，我有一个更改 title 的输入。 field :

const onChange = (e) => {
    setItemInput((prevState) => ({
      ...prevState,
      [e.target.name]: e.target.value,
    }));
  };

这就是 onChange用来:

<input
        type="text"
        className="item-description-input"
        placeholder="Add description..."
        name="title"
        value={itemInput.title}
        onChange={onChange}
      />

GraphQL 端点:

export const CREATE_ITEM = gql`
  mutation createItem($itemInput: ItemInput!) {
    createItem(itemInput: $itemInput) {
      userId
      objectId
      title
      description
      createdAt
    }
  }
`;

提交功能:

const onAddItemClick = (e) => {
    e.preventDefault();
    createItem({
      variables: {
        itemInput: itemInput,
      },
    }).then((res) => {
      console.log(res);
    });
  };

提交时，我得到:

message: "Variable "$itemInput" got invalid value { title: "ddd" }; Field "userId" of required type "MongoId!" was not provided." 

并且对于所有剩余字段重复此错误，但 title .
如果我 console.log(itemInput)当功能组件被加载时，我得到了对象的初始状态。但是，如果我添加 console.log(itemInput)在 onChange 之后, 我只得到 {title: "some_added_text"} . onChange 从对象中删除其他字段，并且在提交时，我的 graphQL 端点返回未提供其他字段的错误。这非常令人沮丧，因为我似乎做的一切都是正确的。
UPD:添加了组件。 Object组件获取对象列表。每个 Object有 Items .有问题的代码在 Items当我想添加一个新的组件时 Item到那个 Object .
对象(父)组件:

import React, { useState, useReactiveVar, Fragment } from "react";
import { useMutation } from "@apollo/client";
import CREATE_OBJECT from "../../mutations/Object";
import { objectsVar } from "../../cache";

//Components
import ItemContainer from "./ItemContainer";

const Container = ({ data, userId, color }) => {
  const [objectInput, setobjectInput] = useState({
    title: "",
    userId: userId,
    createdAt: new Date().getTime().toString(),
    color: color,
  });

  const [createObject] = useMutation(CREATE_OBJECT);

  const onAddClick = (e) => {
    e.preventDefault();
    createObject({
      variables: {
        objectInput: objectInput,
      },
    }).then((res) => {
      setobjectInput({
        title: "",
        userId: userId,
        createdAt: new Date().getTime().toString(),
        color: color,
      });
    });
  };
  
  // This works perfectly fine!! 
  const onChange = (e) => {
    setobjectInput({ ...objectInput, [e.target.name]: e.target.value });
  };

  objectsVar(data);
  const objects = useReactiveVar(objectsVar);

  return (
    <div>
      <div>
        <input
          type="text"
          placeholder="Add description..."
          name="title"
          value={objectInput.title}
          onChange={onChange}
        />
      </div>
      <div onClick={onAddClick}>Add object</div>
      {objects && objects.getAllObjects.length === 0 ? (
        <p>No objects</p>
      ) : (
        <Fragment>
          {objects &&
            objects.getAllActiveSwimlines.map(({ _id, title, items }) => (
              <ItemContainer key={_id} id={_id} title={title} userId={userId} items={items} />
            ))}
        </Fragment>
      )}
    </div>
  );
};

export default Container;

项目(子)组件:

import React, { useState, Fragment } from "react";
import ItemContainer from "../Item/ItemContainer";
import { useMutation } from "@apollo/client";
import { CREATE_ITEM } from "../../mutations/Item";

const ItemContainer = ({ id, title, items, userId }) => {
  const [itemInput, setItemInput] = useState({
    userId: userId,
    objectId: id,
    title: "initial state",
    description: "test desc",
    createdAt: new Date().getTime().toString(),
  });

  // This doesn't work!
  const onChange = (e) => {
    const { name, value } = e.target;
    setItemInput({
      ...itemInput,
      [name]: value,
    });
  };

  const [createItem] = useMutation(CREATE_ITEM);

  const onAddItemClick = (e) => {
    e.preventDefault();
    createItem({
      variables: {
        itemInput: itemInput,
      },
    }).then((res) => {
      setItemInput({
        userId: userId,
        objectId: id,
        title: "",
        description: "",
        createdAt: new Date().getTime().toString(),
      });

      console.log(res);
    });
  };

  const newItemInput = (
    <div>
      <input
        type="text"
        placeholder="Add description..."
        name="title"
        value={itemInput.title}
        onChange={onChange}
      />
      <div onClick={onAddItemClick}>Add item</div>
    </div>
  );

  const itemContent = (
    <div>
      <Fragment>
        {items &&
          items.getObjectItems.map(({ _id, title }) => (
            <Item key={_id} id={_id} title={title} />
          ))}
      </Fragment>
    </div>
  );

  return (
    <div>
      {newItemInput}
      {itemContent}
    </div>
  );
};

export default ItemContainer;

我在这里想念什么？

Answer 1

因为您访问e.target.name和 e.target.value在您的更新函数中，它们不会立即被评估，并且当他们这样做时，合成事件对象已被重用。如果你想保持其余代码不变，你可以通过调用 e.persist() 来修复它。在 onChange 的开头，或复制事件中的相关信息:

  const onChange = (e) => {
    const {name, value} = e.target
    setItemInput((prevState) => ({
      ...prevState,
      [name]: value,
    }));
  };

或者，您可以放开更新功能，直接设置状态，(这在另一个被删除的答案中也有建议):

  const onChange = (e) => {
    setItemInput({
      ...itemInput,
      [e.target.name]: e.target.value,
    });
  };