javascript - 发送许多请求来检查 name 是否存在并设置 name 属性

Question

我有一系列设备。 对于每个设备，我想设置默认名称(“DeviceX” - X 它是一个序列号)，但其中一些可能已被使用/占用。因此，我需要发出请求来检查名称是否已存在(ifDeviceExists() 返回 true 或 false 作为响应)。如果名称已被占用，则应增加编号并再次发送请求以检查该名称(例如“Device2”)是否已存在。如果名称未被占用，则应设置该设备的名称(device.name =“Device2”)。

例如 - 占用的设备名称:“Device2”和“Device4”。那么新创建的设备的名称应该是:“Device1”，“Device3”，“Device5”，“Device6” ... 因此 devices 数组应该是:[{name: "Device1"}, {name: "Device3"}, {name: "Device5"}, {name: "Device6"}, ...]

这里对我来说的主要问题是检查名称是否存在是异步操作，我不知道如何处理它(在哪里发送请求以及何时订阅) 有人可以帮我吗？

Answer 1

  ifDeviceExists(name: string): Observable<boolean> {
    return [ 'Device2', 'Device4' ].includes(name) ? of(true) : of(false);
  }

  findNextDeviceName(indexWrapper: { index: number }, device: Device):
    Observable<{ device: Device, name:string; index: number }> {
    let currentName: string;
    let currentIndex = indexWrapper.index;
    return interval(0).pipe(
      // send requests to check name sequentially until it returns false and filter passes event
      // to first() operator which will stop interval loop, NOTE: if ifDeviceExists() allways returns true,
      // there will be infinite loop
      concatMap(interval => {
        currentIndex = currentIndex + interval;
        currentName = `Device${currentIndex}`;
        return this.ifDeviceExists(currentName);
      }),
      filter(exists => !exists),
      first(),
      map(() => ({device, name: currentName, index: currentIndex})),
    )
  }

  renameDevices(){
    const devices = [{id: 101}, {id: 102}, {id: 103}, {id: 104}];

    // this object keeps last index and allows to change it between concatMap iterations
    const indexWrapper = {index: 1};

    from(devices).pipe(
      concatMap(device => this.findNextDeviceName(indexWrapper, device)),
      map(result => {
        indexWrapper.index = result.index + 1;
        result.device.name = result.name;
        return result.device;
      }),
      toArray()
    ).subscribe({
      next: (devices) => {
        console.log('Devices with names', devices);
      }
    })
  }