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

你想要创建状态的对象

let teams = {
  team: [
    {
      name: "one",
      id: "1"
    },
  ]
}

使团队的状态为对象

const [state, setState] = useState(teams);

像这样更新状态

setState((prevState)=>({...prevState,team:[
     ...prevState.team,
     {
     name: "two",
      id: "2"
     }
]}))

更新后状态变为

{
  team: [
    {
      name: "one",
      id: "1"
    },
    {
      name: "two",
      id: "2"
    }
  ]
}

要渲染项目根据当前状态使用地图功能

{state.team.map((curr_team) => {
      return (
        <div>
           <p>{curr_team.id}</p>
           <p>{curr_team.name}</p>
        </div>
      )
})}

其他回答

一般来说,你应该注意React状态下嵌套很深的对象。为了避免意外的行为,状态应该不可更改地更新。当你有深层对象时,你最终会为了不变性而对它们进行深层克隆,这在React中是相当昂贵的。为什么?

一旦你深度克隆状态,React将重新计算和重新渲染所有依赖于变量的东西,即使它们没有改变!

因此,在尝试解决问题之前,首先考虑如何将状态变平。一旦您这样做了,您就会发现有助于处理大型状态的方便工具,例如useReducer()。

如果你想过,但仍然确信你需要使用深度嵌套的状态树,你仍然可以使用useState()与immutable.js和Immutability-helper等库一起使用。它们使得更新或克隆深层对象变得简单,而不必担心可变性。

谢谢Philip,这帮助了我-我的用例是我有一个有很多输入字段的表单,所以我保持初始状态为对象,我不能更新对象状态。上面的帖子帮助了我:)

const [projectGroupDetails, setProjectGroupDetails] = useState({
    "projectGroupId": "",
    "projectGroup": "DDD",
    "project-id": "",
    "appd-ui": "",
    "appd-node": ""    
});

const inputGroupChangeHandler = (event) => {
    setProjectGroupDetails((prevState) => ({
       ...prevState,
       [event.target.id]: event.target.value
    }));
}

<Input 
    id="projectGroupId" 
    labelText="Project Group Id" 
    value={projectGroupDetails.projectGroupId} 
    onChange={inputGroupChangeHandler} 
/>


我给您留下了一个实用函数来不可变地更新对象

/**
 * Inmutable update object
 * @param  {Object} oldObject     Object to update
 * @param  {Object} updatedValues Object with new values
 * @return {Object}               New Object with updated values
 */
export const updateObject = (oldObject, updatedValues) => {
  return {
    ...oldObject,
    ...updatedValues
  };
};

你可以这样用

const MyComponent = props => {

  const [orderForm, setOrderForm] = useState({
    specialities: {
      elementType: "select",
      elementConfig: {
        options: [],
        label: "Specialities"
      },
      touched: false
    }
  });


// I want to update the options list, to fill a select element

  // ---------- Update with fetched elements ---------- //

  const updateSpecialitiesData = data => {
    // Inmutably update elementConfig object. i.e label field is not modified
    const updatedOptions = updateObject(
      orderForm[formElementKey]["elementConfig"],
      {
        options: data
      }
    );
    // Inmutably update the relevant element.
    const updatedFormElement = updateObject(orderForm[formElementKey], {
      touched: true,
      elementConfig: updatedOptions
    });
    // Inmutably update the relevant element in the state.
    const orderFormUpdated = updateObject(orderForm, {
      [formElementKey]: updatedFormElement
    });
    setOrderForm(orderFormUpdated);
  };

  useEffect(() => {
      // some code to fetch data
      updateSpecialitiesData.current("specialities",fetchedData);
  }, [updateSpecialitiesData]);

// More component code
}

如果没有,您可以在这里找到更多实用程序:https://es.reactjs.org/docs/update.html

,就像这个例子:

首先创建对象的状态:

const [isSelected, setSelection] = useState([{ id_1: false }, { id_2: false }, { id_3: false }]);

然后更改它们的值:

// if the id_1 is false make it true or return it false.

onValueChange={() => isSelected.id_1 == false ? setSelection([{ ...isSelected, id_1: true }]) : setSelection([{ ...isSelected, id_1: false }])}

我认为更优雅的解决方案是创建更新后的状态对象,同时保留以前的state值。需要更新的Object属性可以以这样的数组形式提供

import React,{useState, useEffect} from 'react'
export default function Home2(props) {
    const [x, setX] = useState({name : '',add : {full : '', pin : '', d : { v : '' }}})
    const handleClick = (e, type)=>{
        let obj = {}
        if(type.length > 1){
            var z = {}
            var z2 = x[type[0]]
        
        type.forEach((val, idx)=>{
            if(idx === type.length - 1){
                z[val] = e.target.value
            }
            else if(idx > 0){
                Object.assign(z , z2) /*{...z2 , [val]:{} }*/
                z[val] = {}
                z = z[val]
                z2 = z2[val]
            }else{
                z = {...z2}
                obj = z
            }
        })
    }else obj = e.target.value
    setX( { ...x ,   [type[0]] : obj  } )
    
}
return (
    <div>
        <input value = {x.name} onChange={e=>handleClick(e,["name"])}/>
        <input value = {x.add.full} onChange={e=>handleClick(e,["add","full"])}  />
        <input value = {x.add.pin} onChange={e=>handleClick(e,["add","pin"])}  /><br/>
        <input value = {x.add.d.v} onChange={e=>handleClick(e,["add","d","v"])}  /><br/>
        {x.name} <br/>
        {x.add.full} <br/>
        {x.add.pin} <br/>
        {x.add.d.v}
    </div>
)
}