在嵌套对象中,在React with Hooks中更新状态的正确方法是什么?

export Example = () => {
  const [exampleState, setExampleState] = useState(
  {masterField: {
        fieldOne: "a",
        fieldTwo: {
           fieldTwoOne: "b"
           fieldTwoTwo: "c"
           }
        }
   })

如何使用setExampleState将exampleState更新为a(附加字段)?

const a = {
masterField: {
        fieldOne: "a",
        fieldTwo: {
           fieldTwoOne: "b",
           fieldTwoTwo: "c"
           }
        },
  masterField2: {
        fieldOne: "c",
        fieldTwo: {
           fieldTwoOne: "d",
           fieldTwoTwo: "e"
           }
        },
   }
}

b(改变值)?

const b = {masterField: {
        fieldOne: "e",
        fieldTwo: {
           fieldTwoOne: "f"
           fieldTwoTwo: "g"
           }
        }
   })

当前回答

答案已经有了,但是这种类型没有被提到,所以看看这种类型的例子…

 const[data,setdata]= useState({
    username: [
      email,
      "required", 
      //...some additional codes
    ],
    password: [
      password,
      "required|password-5",
     //..additional code if any..
    ],
  })

**要在输入字段中更新状态变量email,您可以添加类似的代码与您的变量名**

          <Input
              onChangeText={(t) => setdata(prevState=>({...prevState,username:{[0]:t}}))}
              value={data.username[0]}
            />

其他回答

最初我在useState中使用object,但后来我移动到useReducer钩子用于复杂的情况。重构代码时,我感到性能有所提高。

当您有涉及多个子值的复杂状态逻辑时,或者当下一个状态依赖于前一个状态时,useReducer通常比useState更可取。

useReducer React文档

我已经实现了这样的钩子供我自己使用:

/**
 * Same as useObjectState but uses useReducer instead of useState
 *  (better performance for complex cases)
 * @param {*} PropsWithDefaultValues object with all needed props 
 * and their initial value
 * @returns [state, setProp] state - the state object, setProp - dispatch 
 * changes one (given prop name & prop value) or multiple props (given an 
 * object { prop: value, ...}) in object state
 */
export function useObjectReducer(PropsWithDefaultValues) {
  const [state, dispatch] = useReducer(reducer, PropsWithDefaultValues);

  //newFieldsVal={[field_name]: [field_value], ...}
  function reducer(state, newFieldsVal) {
    return { ...state, ...newFieldsVal };
  }

  return [
    state,
    (newFieldsVal, newVal) => {
      if (typeof newVal !== "undefined") {
        const tmp = {};
        tmp[newFieldsVal] = newVal;
        dispatch(tmp);
      } else {
        dispatch(newFieldsVal);
      }
    },
  ];
}

更多相关的钩子。

你可以像这样传递新值:

  setExampleState({...exampleState,  masterField2: {
        fieldOne: "a",
        fieldTwo: {
           fieldTwoOne: "b",
           fieldTwoTwo: "c"
           }
        },
   })

我认为最好的解决办法是Immer。它允许你像直接修改字段一样更新对象(masterField.fieldOne。Fieldx = 'abc')。但它当然不会改变实际对象。它收集草稿对象上的所有更新,并在最后为您提供一个最终对象,您可以使用它来替换原始对象。

如果有人正在搜索useState()钩子,则更新为对象

- Through Input

        const [state, setState] = useState({ fName: "", lName: "" });
        const handleChange = e => {
            const { name, value } = e.target;
            setState(prevState => ({
                ...prevState,
                [name]: value
            }));
        };

        <input
            value={state.fName}
            type="text"
            onChange={handleChange}
            name="fName"
        />
        <input
            value={state.lName}
            type="text"
            onChange={handleChange}
            name="lName"
        />
   ***************************

 - Through onSubmit or button click
    
        setState(prevState => ({
            ...prevState,
            fName: 'your updated value here'
         }));

我迟到了。:)

@aseferov回答在意图是重新进入整个对象结构时非常有效。然而,如果目标/目标是更新Object中的特定字段值,我认为下面的方法更好。

情境:

const [infoData, setInfoData] = useState({
    major: {
      name: "John Doe",
      age: "24",
      sex: "M",
    },

    minor:{
      id: 4,
      collegeRegion: "south",

    }

  });

更新特定的记录需要回调到之前的状态prevState

在这里:

setInfoData((prevState) => ({
      ...prevState,
      major: {
        ...prevState.major,
        name: "Tan Long",
      }
    }));

也许

setInfoData((prevState) => ({
      ...prevState,
      major: {
        ...prevState.major,
        name: "Tan Long",
      },
      minor: {
        ...prevState.minor,
        collegeRegion: "northEast"

    }));

我希望这对试图解决类似问题的人有所帮助。