# 全局配置项功能场景

对于需要使用进程单例的场景，例如不同并发实例间需要数据保持一致的全局配置项功能，可以采用共享模块来实现。

以下示例展示了只有在Wi-Fi打开且用户登录的情况下才能进行下载的功能，具体步骤如下。

1.  编写全局配置文件。
    
    ```
    import { ArkTSUtils } from '@kit.ArkTS';
    
    'use shared'
    
    @Sendable
    class Config {
      public lock: ArkTSUtils.locks.AsyncLock = new ArkTSUtils.locks.AsyncLock();
      public isLogin: boolean = false;
      public loginUser?: string;
      public wifiOn: boolean = false;
    
      async login(user: string) {
        return this.lock.lockAsync(() => {
          this.isLogin = true;
          this.loginUser = user;
        }, ArkTSUtils.locks.AsyncLockMode.EXCLUSIVE)
      }
    
      async logout(user?: string) {
        return this.lock.lockAsync(() => {
          this.isLogin = false;
          this.loginUser = '';
        }, ArkTSUtils.locks.AsyncLockMode.EXCLUSIVE)
      }
    
      async getIsLogin(): Promise<boolean> {
        return this.lock.lockAsync(() => {
          return this.isLogin;
        }, ArkTSUtils.locks.AsyncLockMode.SHARED)
      }
    
      async getUser(): Promise<string> {
        return this.lock.lockAsync(() => {
          return this.loginUser!;
        }, ArkTSUtils.locks.AsyncLockMode.SHARED)
      }
    
      async setWifiState(state: boolean) {
        return this.lock.lockAsync(() => {
          this.wifiOn = state;
        }, ArkTSUtils.locks.AsyncLockMode.EXCLUSIVE)
      }
    
      async isWifiOn() {
        return this.lock.lockAsync(() => {
          return this.wifiOn;
        }, ArkTSUtils.locks.AsyncLockMode.SHARED)
      }
    }
    
    export let config = new Config();
    ```
    
2.  UI主线程及子线程访问全局配置项。
    
    ```
    import { config } from './Config';
    import { taskpool } from '@kit.ArkTS';
    
    @Concurrent
    async function download() {
      if (!await config.isWifiOn()) {
        console.info('wifi is off');
        return false;
      }
      if (!await config.getIsLogin()) {
        console.info('not login');
        return false;
      }
      console.info(`User[${await config.getUser()}] start download ...`);
      return true;
    }
    
    @Entry
    @Component
    struct Index {
      @State message: string = 'not login';
      @State wifiState: string = 'wifi off';
      @State downloadResult: string = '';
      input: string = '';
    
      build() {
        Row() {
          Column() {
            Text(this.message)
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
            TextInput({ placeholder: '请输入用户名' })
              .id('textInput')
              .fontSize(20)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
              .onChange((value) => {
                this.input = value;
              })
            Text('login')
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
              .onClick(async () => {
                if (!await config.getIsLogin() && this.input) {
                  try {
                    await config.login(this.input);
                    this.message = 'login: ' + this.input;
                  } catch (e) {
                    console.error('login failed');
                  }
                }
              })
              .backgroundColor(0xcccccc)
            Text('logout')
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
              .onClick(async () => {
                if (await config.getIsLogin()) {
                  try {
                    await config.logout();
                    this.message = 'not login';
                  } catch (e) {
                    console.error('logout failed');
                  }
                }
              })
              .backgroundColor(0xcccccc)
            Text(this.wifiState)
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
            Toggle({ type: ToggleType.Switch })
              .onChange(async (isOn: boolean) => {
                await config.setWifiState(isOn)
                this.wifiState = isOn ? 'wifi on' : 'wifi off';
              })
            Text('download')
              .fontSize(50)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
              .onClick(async () => {
                let ret = await taskpool.execute(download);
                this.downloadResult = ret ? 'download success' : 'download fail';
              })
            Text(this.downloadResult)
              .fontSize(20)
              .fontWeight(FontWeight.Bold)
              .alignRules({
                center: { anchor: '__container__', align: VerticalAlign.Center },
                middle: { anchor: '__container__', align: HorizontalAlign.Center }
              })
          }
          .width('100%')
        }
        .height('100%')
      }
    }
    ```