How to pass object as pointer - C++ syntax ?

Anonymous_Banned275

This is plain C++ question I am struggling with, nothing to do with Qt

I like to have MainWindow Widget to list local bluetooth device info.
I have build a class to retrieve the info, now I need MainWindow to access it. .
I just cannot figure out the correct syntax how to pass / retrieve / use the list pointer to my object / class so I can use it in MainWindow .

Here are snippets of my code

This class uses QList , QBluetoothHostInfo and QBluetoothLocalDevice and works as expected returning "infos" - locally for test purpose.

CCC_LocalAdapters::CCC_LocalAdapters(QObject *parent) : QObject(parent)
{

// get bluetooth device information
// bluetooth test for local device - works as expected locally
QList<QBluetoothHostInfo> infos = QBluetoothLocalDevice::allDevices();
…
}

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
...
// build instance of class , pass object pointer
CCC_LocalAdapters *LocalAdapters = new CCC_LocalAdapters(infos);

this syntax / usage is wrong and I am getting this compiler error

/home/f/QT_PROJECT/TEST_PROJECT_3/mainwindow.cpp:60: error: missing template arguments before 'infos'
 CCC_LocalAdapters *LocalAdapters_info = new CCC_LocalAdapters(QList infos);
                                                                     ^

...
I did try this

CCC_LocalAdapters *LocalAdapters_info = new CCC_LocalAdapters(QList<QBluetoothHostInfo> infos);

And getting this error

/home/f/QT_PROJECT/TEST_PROJECT_3/mainwindow.cpp:60: error: expected primary-expression before 'infos'
 CCC_LocalAdapters *LocalAdapters_info = new CCC_LocalAdapters(QList<QBluetoothHostInfo> infos);
                                                                                         ^

I am totally lost. Please help C++ ignorant person .

}

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    //add 21/11/2020
    // local BT device info
    QList<QBluetoothHostInfo> *infos;
   ….
   }

In not so technical terms – I need to pass “infos” upstream so I can let main
window GUI print it.

SGaist

Hi,

@AnneRanch said in How to pass object as pointer - C++ syntax ?:

CCC_LocalAdapters

The only constructor you have take a QObject as parameter.

Add a getter to that class that returns the internal list you store in it.

Pl45m4

@AnneRanch

So you want that info QList from CCC_LocalAdapters in your MainWindow class?!

You can either make that info list in CCC_LocalAdapters public by declaring it as public member variable in CCC_LocalAdapters header
OR
you add a public function ("getter"), that returns the (private) member (e.g. as reference) ( @SGaist's approach) .

Something like:

// ####### CCC_LocalAdapters.h ###########
public:
QList< QBluetoothHostInfo > & getInfoList();

private:
QList< QBluetoothHostInfo > info;

// ####### CCC_LocalAdapters.cpp ###########
QList<QBluetoothHostInfo>& CCC_LocalAdapters::getInfoList(){
        return info;
}

Then you can do something like this in your MainWindow class:

CCC_LocalAdapters *LocalAdapters = new CCC_LocalAdapters();
info = LocalAdapters->getInfoList(); // will return a reference to that list in CC_LocalAdapters

Anonymous_Banned275

@AnneRanch said in How to pass object as pointer - C++ syntax ?:

CCC_LocalAdapters::CCC_LocalAdapters(QObject *parent) : QObject(parent)

Thanks fellas.

So you want that info QList from CCC_LocalAdapters in your MainWindow class?!
Yes, that is my goal.
I though I had it using the "second" solution.
I'll digest you suggestions and report back later. I am "nursing" my bedridden partner - broken leg and wrist - so have not much time to bang on the keyboard.
Later