CODEWITHSUNDEEP
c++visual-studio-2010pointersvector
page47250
page47250

Reputation: 311

Pointer to vector of structs error

I'm making a .lib file for a mobile robot. Currently I'm writing a function for scanning Bluetooth devices.

The function is:

struct Device
{
     string DeviceName;
     BTH_ADDR DeviceAddress;
};

void ScanForDevices(vector<Device> *Robot)
    {
        m_bt = BluetoothFindFirstRadio(&m_bt_find_radio, &m_radio);

        BluetoothGetRadioInfo(m_radio, &m_bt_info);
        m_search_params.hRadio = m_radio;

        ZeroMemory(&m_device_info, sizeof(BLUETOOTH_DEVICE_INFO));
        m_device_info.dwSize = sizeof(BLUETOOTH_DEVICE_INFO);

        m_bt_dev = BluetoothFindFirstDevice(&m_search_params, &m_device_info);


        int m_device_id = 0;
        char charDeviceName[250];

        do {
                charDeviceName[250]=NULL;
                Robot->push_back(Device()); 
                //WideCharToMultiByte(CP_UTF8,0,m_device_info.szName,-1, charDeviceName,0,NULL, NULL);
                WideCharToMultiByte(CP_UTF8,0,m_device_info.szName,-1, charDeviceName,250,NULL, NULL);
                Robot[m_device_id]->DeviceName=(string)charDeviceName;
                Robot[m_device_id]->DeviceAddress=m_device_info.Address.ullLong;
                m_device_id++;

            } while(BluetoothFindNextDevice(m_bt_dev,&m_device_info));

            BluetoothFindDeviceClose(m_bt_dev);

            BluetoothFindRadioClose(m_bt);
    }

I keep getting:

Error   6   error C2819: type 'std::vector<_Ty>' does not have an overloaded member 'operator ->'
Error   7   error C2039: 'DeviceName' : is not a member of 'std::vector<_Ty>'
Error   8   error C2819: type 'std::vector<_Ty>' does not have an overloaded member 'operator ->'
Error   9   error C2039: 'DeviceAddress' : is not a member of 'std::vector<_Ty>'
Error   10  IntelliSense: expression must have pointer type 
Error   11  IntelliSense: expression must have pointer type

I'm starting C++ and am not really skilled in the use of pointers.

Any help is welcomed.

Upvotes: 0

Views: 1315

Answers (2)

billz
billz

Reputation: 45410

Robot is a pointer points to vector<Device>. You are confusing yourself with point to vector and vector element accessing. To fix the issue, you could change:

Robot[m_device_id]->DeviceName=(string)charDeviceName;

to

Robot->at(m_device_id).DeviceName = std::string(charDeviceName);

Or

(*Robot)[m_device_id].DeviceName = std::string(charDeviceName);

Suggestion:

Better solution is to pass vector by reference instead of pointer.

void ScanForDevices(vector<Device> &Robot)
{
    std::string  charDeviceName;   //<<-- use std::string instead of char array
    Robot[m_device_id].DeviceName = charDeviceName;  //<<-- this is better coding style
}

Upvotes: 1

Alex F
Alex F

Reputation: 43311

To access vector<Device> *Robot element by index, use the following syntax:

(*Robot)[m_device_id]

Your code should be:

(*Robot)[m_device_id].DeviceName=(string)charDeviceName;

Note that -> is replaced by . because the vector element has Device type, this is not pointer.

Your existing code matches the following vector declaration: 

vector<Device*> Robot

See the difference.

Upvotes: 1

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