防止在父组件状态更改后重置子状态也可以获取所有子组件的值：ReactJS + Typescript

Question

我对反应有点陌生，在这种情况下，我将为React中的表实现自定义下拉过滤器。 我为每列设置了下拉值，并且有一个“应用”按钮。

我为此维护了一个子组件，该组件接收下拉值并将选定的子组件发送回父组件。 然后，我调用一个后端API，该API向我提供过滤后的数据，这些数据依次设置了父状态。 这里的问题是在获取数据并设置父状态后，下拉列表中的复选框值丢失了。

每个子组件都有一组复选框，一个“应用”和一个清除按钮。 因此，在单击“应用”时，我必须将选中的对象发送给父级，或者通常将选中的对象发送给父对象，而不会丢失先前的内容。

我不明白为什么我会丢失复选框值？

如果有人可以帮助我，这将有很大的帮助

沙盒： https ： //codesandbox.io/s/nervous-elgamal-0zztb

我在沙盒链接中添加了适当的注释。 请看一看。 我有点新反应。

帮助将不胜感激

父级

import * as React from "react";
import { render } from "react-dom";
import ReactTable from "react-table";
import "./styles.css";
import "react-table/react-table.css";
import Child from "./Child";
interface IState {
  data: {}[];
  columns: {}[];
  selectedValues: {};
  optionsForColumns: {};
}

interface IProps {}

export default class App extends React.Component<IProps, IState> {

  // Here I have  hardcoded the values, but data and optionsForColumns comes from the backend and it is set inside componentDidMount
  constructor(props: any) {
    super(props);
    this.state = {
      data: [
        { firstName: "Jack", status: "Submitted", age: "14" },
        { firstName: "Simon", status: "Pending", age: "15" }
      ],
      selectedValues: {},
      columns: [],
      optionsForColumns: {
        firstName: [{ Jack: "4" }, { Simon: "5" }],
        status: [{ Submitted: "5" }, { Pending: "7" }]
      }
    };
  }

  // Get the values for checkboxes that will be sent to child
  getValuesFromKey = (key: any) => {
    let data: any = this.state.optionsForColumns[key];
    let result = data.map((value: any) => {
      let keys = Object.keys(value);
      return {
        field: keys[0],
        checked: false
      };
    });
    return result;
  };

  // Get the consolidated values from child and then pass it for server side filtering
  handleFilter = (fieldName: any, selectedValue: any, modifiedObj: any) => 
  {
    this.setState(
      {
        selectedValues: {
          ...this.state.selectedValues,
          [fieldName]: selectedValue
        }
      },
      () => this.handleColumnFilter(this.state.selectedValues)
    );
  };

  // Function that will make server call based on the checked values from child
  handleColumnFilter = (values: any) => {
    // server side code for filtering
    // After this checkbox content is lost
  };

  // Function where I configure the columns array for the table . (Also data and column fiter values will be set here, in this case I have hardcoded inside constructor)
  componentDidMount() {
    let columns = [
      {
        Header: () => (
          <div>
            <div>
              <Child
                key="firstName"
                name="firstName"
                options={this.getValuesFromKey("firstName")}
                handleFilter={this.handleFilter}
              />
            </div>
            <span>First Name</span>
          </div>
        ),
        accessor: "firstName"
      },
      {
        Header: () => (
          <div>
            <div>
              <Child
                key="status"
                name="status"
                options={this.getValuesFromKey("status")}
                handleFilter={this.handleFilter}
              />
            </div>
            <span>Status</span>
          </div>
        ),
        accessor: "status",
      },
      {
        Header: "Age",
        accessor: "age"
      }
    ];
    this.setState({ columns });
  }

  //Rendering the data table
  render() {
    const { data, columns } = this.state;
    return (
      <div>
        <ReactTable
          data={data}
          columns={columns}
        />
      </div>
    );
  }
}
const rootElement = document.getElementById("root");
render(<App />, rootElement);

儿童

import * as React from "react";
import { Button, Checkbox, Icon } from "semantic-ui-react";
interface IProps {
  options: any;
  name: string;
  handleFilter(val1: any, val2: any, val3: void): void;
}
interface IState {
  showList: boolean;
  selected: [];
  checkboxOptions: any;
}
export default class Child extends React.Component<IProps, IState> {
  constructor(props: any) {
    super(props);
    this.state = {
      selected: [],
      showList: false,
      checkboxOptions: this.props.options.map((option: any) => option.checked)
    };
  }

  // Checkbox change handler
  handleValueChange = (event: React.FormEvent<HTMLInputElement>, data: any) => {
    const i = this.props.options.findIndex(
      (item: any) => item.field === data.name
    );
    const optionsArr = this.state.checkboxOptions.map(
      (prevState: any, si: any) => (si === i ? !prevState : prevState)
    );
    this.setState({ checkboxOptions: optionsArr });
  };

  //Passing the checked values back to parent
  passSelectionToParent = (event: any) => {
    event.preventDefault();
    const result = this.props.options.map((item: any, i: any) =>
      Object.assign({}, item, {
        checked: this.state.checkboxOptions[i]
      })
    );
    const selected = result
      .filter((res: any) => res.checked)
      .map((ele: any) => ele.field);
    console.log(selected);
    this.props.handleFilter(this.props.name, selected, result);
  };

  //Show/Hide filter
  toggleList = () => {
    this.setState(prevState => ({ showList: !prevState.showList }));
  };

  //Rendering the checkboxes based on the local state, but still it gets lost after filtering happens
  render() {
    let { showList } = this.state;
    let visibleFlag: string;
    if (showList === true) visibleFlag = "visible";
    else visibleFlag = "";
    return (
      <div>
        <div style={{ position: "absolute" }}>
          <div
            className={"ui scrolling dropdown column-settings " + visibleFlag}
          >
            <Icon className="filter" onClick={this.toggleList} />
            <div className={"menu transition " + visibleFlag}>
              <div className="menu-item-holder">
                {this.props.options.map((item: any, i: number) => (
                  <div className="menu-item" key={i}>
                    <Checkbox
                      name={item.field}
                      onChange={this.handleValueChange}
                      label={item.field}
                      checked={this.state.checkboxOptions[i]}
                    />
                  </div>
                ))}
              </div>
              <div className="menu-btn-holder">
                <Button size="small" onClick={this.passSelectionToParent}>
                  Apply
                </Button>
              </div>
            </div>
          </div>
        </div>
      </div>
    );
  }
}

Answer 1

这似乎是状态管理不便的情况。 当前，状态在子级进行管理，但在父级进行管理将更加容易。 这在React中被称为提升状态 。

要点-共享状态在父组件中进行管理，并通过调用传递给子组件的函数来对其进行更新。 单击“应用”后，选定的单选值将传递到“父级”，“父级”会将新选择合并到共享状态。

我创建了一个最小的代码示例，展示了如何将状态从子级提升到父级。 我还使用了React的一些新功能，例如useState来简化Child组件。

 // Child Component const Child = ({name, options, updateSelections}) => { const [selected, setSelected] = React.useState([]); const handleChange = (event) => { let updated; if (event.target.checked) { updated = [...selected, event.target.value]; } else { updated = selected.filter(v => v !== event.target.value); } setSelected(updated); } const passSelectionToParent = (event) => { event.preventDefault(); updateSelections(name, selected); } return ( <form> {options.map(item => ( <label for={name}> <input key={name} type="checkbox" name={item} value={item} onChange={handleChange} /> {item} </label> ))} <button onClick={passSelectionToParent}>Apply</button> </form> ) } // Parent Component class Parent extends React.Component { constructor(props) { super(props); this.fields = ["firstName", "status"], this.state = { selected: {} }; } getValuesFromKey = (data, key) => { return data.map(item => item[key]); } updateSelections = (name, selection) => { this.setState({ selected: {...this.state.selected, [name]: selection} }, () => console.log(this.state.selected)); } render() { return ( <div> {this.fields.map(field => ( <Child key={field} name={field} options={this.getValuesFromKey(this.props.data, field)} updateSelections={this.updateSelections} /> ))} </div> ) } } const data = [ { firstName: "Jack", status: "Submitted" }, { firstName: "Simon", status: "Pending" }, { firstName: "Pete", status: "Approved" }, { firstName: "Lucas", status: "Rejected" } ]; ReactDOM.render(<Parent data={data}/>, document.getElementById("root")); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.7.0-alpha.2/umd/react.production.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.7.0-alpha.2/umd/react-dom.production.min.js"></script> <div id="root"></div> 

Answer 2

仅当您隐藏/显示表时，复选框值才会丢失，因为表从DOM中移出时，其状态以及其子级都将丢失。 将表安装到DOM时，再次安装Child组件，以从getValuesFromKey方法获取复选框值的状态初始化一个新状态，默认情况下，该值将返回false，清除复选框的刻度。

return {
  field: keys[0],
  checked: false
};

Stackblitz重现了该问题 。

您必须设置复选框值，以检查selectedValues对象以查看是否已选中它。

return {
  field: keys[0],
  checked: this.state.selectedValues[key] && this.state.selectedValues[key].includes(keys[0]),
};