Base classes should have virtual destructors

  // Default constructor initializes all fields to be empty/false.

  AdvertiseData();

  AdvertiseData(const AdvertiseData& other);

  ~AdvertiseData() = default;

  virtual ~AdvertiseData() = default;

  // Returns true if the advertising data is formatted correctly according to

  // the TLV format.

  //   TX power level: TX_POWER_LEVEL_MEDIUM

  //   connectable: true

  AdvertiseSettings();

  ~AdvertiseSettings() = default;

  virtual ~AdvertiseSettings() = default;

  // Returns the advertise mode.

  Mode mode() const { return mode_; }

        permissions_(permissions),

        descriptors_(descriptors){};

  Characteristic& operator=(const Characteristic& other);

  ~Characteristic() = default;

  virtual ~Characteristic() = default;

  // Comparison function and operator.

  bool Equals(const Characteristic& other) const;

  Descriptor& operator=(const Descriptor& other);

  Descriptor(uint16_t handle, const UUID& uuid, uint16_t permissions)

      : handle_(handle), uuid_(uuid), permissions_(permissions){};

  ~Descriptor() = default;

  virtual ~Descriptor() = default;

  // Comparison function and operator.

  bool Equals(const Descriptor& other) const;

class ScanFilter {

 public:

  ScanFilter() = default;

  ~ScanFilter() = default;

  virtual ~ScanFilter() = default;

  // Copy constructor and assignment operator.

  ScanFilter(const ScanFilter& other);