当 promise 解决时如何重新渲染 React 组件？ |如何在数据加载之前阻止渲染？

Question

我尝试更新指向azure-devops-ui/Filter 的功能组件。我正在使用返回异步响应的azure-devops-extension-sdk，以便使用此组件：
https://developer.microsoft.com/en-us/azure-devops/components/filter Azure DevOps 上的 WorkItem 内

我已经分别使用 this.state/componentDidMount 和 useState/useEffect 编写了基于类和函数组件的代码。我关注了this SO post。

但是，我只能重新渲染状态。状态更新时，类和功能组件中的 UI 组件都不会更新。

我的代码有两个版本，它们都在等待响应并成功更新状态。但是，两者都不会等待 UI 的呈现。

通用组件：

import {
    IWorkItemChangedArgs,
    IWorkItemFieldChangedArgs,
    IWorkItemFormService,
    IWorkItemLoadedArgs,
    WorkItemTrackingServiceIds,
  } from "azure-devops-extension-api/WorkItemTracking";

import * as React from "react";
import * as SDK from "azure-devops-extension-sdk";

import { Header } from "azure-devops-ui/Header";
import { Page } from "azure-devops-ui/Page";

import { Filter, getKeywordFilterItem } from "azure-devops-ui/Filter";
import { IListBoxItem } from "azure-devops-ui/ListBox";
import { AggregateItemProvider } from "azure-devops-ui/Utilities/AggregateItemProvider";
import {
    Filter as FilterStore,
    FILTER_CHANGE_EVENT,
    IFilterState
} from "azure-devops-ui/Utilities/Filter";
import { GroupedItemProvider } from "azure-devops-ui//Utilities/GroupedItemProvider";
import { groupedItems, groups, statusItems } from "./data";
        export class WorkItemComponent extends React.Component<{} & ExtendedProps, any> {

    private provider: AggregateItemProvider<IListBoxItem>;

    private filterStore = new FilterStore();

    private textoStore = "second";

    private groupedProvider = new GroupedItemProvider([], [], true);
    private filterItems = [
        getKeywordFilterItem(this.filterStore),
        { name: "Status", id: "status", items: statusItems, filterItemKey: "status" },
        {
            name: "Group Items",
            id: "groupItems",
            items: this.groupedProvider,
            filterItemKey: "groupItems"
        }
    ];

    constructor(props: {}) {
        super(props);
        this.provider = new AggregateItemProvider<IListBoxItem>();
        this.groupedProvider.push(...groupedItems);
        this.groupedProvider.pushGroups(...groups);
        this.provider.push(statusItems);
        this.provider.push(this.groupedProvider);


        if(this.props.pdata==="first")
        this.filterStore = new FilterStore(
          {defaultState: {    groupItems: {        value: [this.props.pdata,this.textoStore]    }}} 
          );
          else
          this.filterStore = new FilterStore(
            {defaultState: {    groupItems: {        value: [this.textoStore,this.props.pdata,]    }}} 
            );


          this.filterStore.subscribe(this.onFilterChanged, FILTER_CHANGE_EVENT);


        this.state = {
            //currentState: ""
            currentState: JSON.stringify(this.filterStore.getState(), null, 4)
        };

    }

    public render():JSX.Element {

        return (
            <Page className="sample-hub flex-grow">
                <Header title="Filter" />
                <div className="page-content">
                <Filter 
                    filterStore={this.filterStore}
                    filterItems={this.filterItems}
                    items={this.provider}
                />
                    <div style={{ marginTop: "16px" }} className="monospaced-text">
                        <span>Current state:</span>
                        <span>{this.state.currentState}</span>
                        <span>{this.props.pdata}</span>
                    </div>
                </div>
            </Page>
        );
    }

    private onFilterChanged = (changedState: IFilterState) => {
        this.setState({
            currentState: JSON.stringify(this.filterStore.getState(), null, 4)
        });
        this.onFilterChangedExtended(JSON.stringify(this.filterStore.getState(), null, 4))
    };

    private async onFilterChangedExtended(estadoActual: string) {
        const workItemFormService = await SDK.getService<IWorkItemFormService>(
          WorkItemTrackingServiceIds.WorkItemFormService
        );

        workItemFormService.setFieldValue(SDK.getConfiguration().witInputs.FieldName, estadoActual);

      }

Functional 组件中第一个具有 useState 和 useEffect 的 Caller：

        import { WorkItemComponent } from "./WorkItemComponent";

  const WorkItemFilterAsync: React.FC = props => {

    let respuestaAsync="";

    const [data, setData] = React.useState<string>('');
    React.useEffect(() => {
    const fetchdata = async() =>{
      const result = await fngetFieldName()

         setData(result);

    }      
      // Execute the created function directly
      fetchdata();

    }, []);


    async function fngetFieldName(): Promise<string> {
      const workItemFormService = await SDK.getService<IWorkItemFormService>(
        WorkItemTrackingServiceIds.WorkItemFormService
      );

      const respuesta = workItemFormService.getFieldValue(SDK.getConfiguration().witInputs.FieldName);
      respuestaAsync = (await respuesta).toString();
      return JSON.stringify(respuesta);
    }
  return <WorkItemComponent pdata={data}/>
}
export default WorkItemFilterAsync;

第二个调用者在一个类上有componentDidMount：

import {
    IWorkItemChangedArgs,
    IWorkItemFieldChangedArgs,
    IWorkItemFormService,
    IWorkItemLoadedArgs,
    WorkItemTrackingServiceIds,
  } from "azure-devops-extension-api/WorkItemTracking";


import * as React from "react";
import { showRootComponent } from "../../Common";
import * as SDK from "azure-devops-extension-sdk";

import { WorkItemComponent } from "./WorkItemComponent";

//const WorkItemComponent = React.lazy (() => import('./WorkItemComponent'));


class WorkItemFilter extends React.Component{
    state = {
        externalData: false,
      };

      public componentDidMount() {
          this.onLoadExtended();
    }

    render():JSX.Element {

            return(

                <div className="page-content">
                    {this.state.externalData ? <WorkItemComponent pdata="first"/> : <WorkItemComponent pdata="third"/>}
                </div>

            );
        }


        private async onLoadExtended() {
            const workItemFormService = await SDK.getService<IWorkItemFormService>(
              WorkItemTrackingServiceIds.WorkItemFormService
            );

            let varaux = workItemFormService.getFieldValue(SDK.getConfiguration().witInputs.FieldName);

            if ((await varaux).toString()!=="")
            {

                this.setState({
                    externalData: true,
                });

            }

          }


}


  showRootComponent(<WorkItemFilter />);

这是父组件：

export function showRootComponent(component: React.ReactElement<any>) {
    ReactDOM.render(component, document.getElementById("root"));
}

Azure Dev Ops Extension (azure-devops-extension.json) 的配置：

{
    "contributions": [
        {
            "id": "work-item-filter",
            "type": "ms.vss-work-web.work-item-form-control",
            "description": "Custom Filter",
            "targets": [
                "ms.vss-work-web.work-item-form"
            ],
            "properties": {
                "name": "BHD Filter",
                "uri": "dist/WorkItemFilter/WorkItemFilter.html",
                "height": 600,
                "inputs": [
                    {
                        "id":"FieldName",
                        "name": "Select the field for this control.",
                        "type": "WorkItemField",
                        "properties": {
                            "workItemFieldTypes": ["String", "PlainText", "HTML"]
                        },
                        "validation": {
                            "dataType": "String",
                            "isRequired": true
                        }

我也尝试将ReactDOM.render 放在浏览器事件中，但我不能这样做，因为 UI 扩展需要一个字段来保存数据：

Answer 1

使用新的 React Hooks 编写功能性反应组件很简单。在下面的示例中，我使用useState 和useEffect。 useState 钩子与基于类的 React 组件中的 this.state/this.setState 同义。 useEffect 钩子类似于componentDidMount+componentDidUpdate。它也可以是componentDidUnmount。

代码的执行方式是从上到下。因为它是函数式的，所以它会运行一次并以useState 的参数中设置的默认状态进行渲染。它不会阻止从 useEffect 函数中的 API 获取数据。因此，您需要能够在没有数据的情况下处理加载。任何时候props.apiConfig 或props.id 发生变化，组件都会重新渲染，所有useEffect 都会重新渲染。 如果props.apiConfig 和props.id 在第一次运行后发生变化，它只会调用useEffect。 唯一讨厌的部分是useEffect 不能是async 函数，所以你必须调用函数getDataWrapper 不使用await。当API接收到数据后，会将数据存储在state中，这会触发组件的重新渲染。

总结：

1. 使用默认状态渲染一次
   • 呼叫useEffect，后者呼叫getDataWrapper
   • 返回初始值在useState中的组件
2. 一旦API在useEffect/getDataWrapper函数中接收到数据，通过setState设置状态并将isLoading设置为false
3. 使用setState 现在包含的更新值重新渲染组件
   • 避免使用useEffect 控制路径，因为useEffect 的第二个参数中的值没有改变。 （例如：props.apiConfig & props.id）。

import React, { useState, useEffect } from 'react';
import { getDataFromAPI } from './api';

const MyComponent = (props) => {

  const [state, useState] = useState({
    isLoading: true,
    data: {}
  });

  useEffect(() => {
    const getDataWrapper = async () => {
      const response = await getDataFromAPI(apiConfig, props.id);
      setState({
        isLoading: false,
        data: response
      });
    });

    getDataWrapper();
  }, [props.apiConfig, props.id]);


  if(state.isLoading) { return <div>Data is loading from API...</div>

  return (
    <div>
      <h1>Hello, World!</h1>
      <pre>{JSON.stringify(state.data, null, 2)}</pre>
    </div>
  );
};

export default MyComponent;