problem creating QAbstractItemModel

mzimmers

Hi all -

This is only my 2nd time working in the model/view world. I was trying to use the code from my 1st time as a, well, you know...model.

I want to populate a model with data I receive from a TCP message. I have a class containing the model:

model_ap_scan.h

class ModelApScan : public QObject
{
    Q_OBJECT
private:
    QAbstractItemModel *m_model;    // the main model
public:
    explicit ModelApScan(QObject *parent = Q_NULLPTR);
    ~ModelApScan();
public slots:
    void update(Message *msg, vector<string> &keys);

model_ap_scan.cpp:

ModelApScan::ModelApScan(QObject *parent) : QObject(parent), m_model(new QStandardItemModel(this))
{
    m_model->insertColumns(0, AP_TABLE_NBR_COLUMNS);
    m_model->setHeaderData(AP_TABLE_COLUMN_MACADDR, Qt::Horizontal, tr("MAC Address"), Qt::DisplayRole);
    m_model->setHeaderData(AP_TABLE_COLUMN_SSID, Qt::Horizontal, tr("SSID"), Qt::DisplayRole);
    m_model->setHeaderData(AP_TABLE_COLUMN_RSSI, Qt::Horizontal, tr("RSSI"), Qt::DisplayRole);
}

void ModelApScan::update(Message *msg, vector<string> &keys)
{
    int row;
    int rowCnt = m_model->rowCount();
...

This is, as far as I can see, verbatim from my 1st model. But, I get a segfault on the call to rowCount() in update(). Can anyone see what I'm doing wrong?

Thanks...

KillerSmath

@mzimmers
I've implemented your snippet and everything is working fine.

Can you share with us an extended snippet ? Maybe, the problem is in way that you insert the Items in the Model.

jsulm

@mzimmers said in problem creating QAbstractItemModel:

I get a segfault on the call to rowCount()

If you get a segfault there then it means m_model is invalid pointer.
Do you delete m_model somewhere?

mzimmers

@KillerSmath hi - I'm not inserting any items yet. My model is empty when I make that call.

@jsulm no, I'm not deleting it, but...in stepping through the debugger, I just realized that my c'tor isn't being called. That's really odd...don't know what to make of that, though it does explain why the call to rowCount() blows up.

SGaist

Hi,

Where are you creating the instance of ModelApScan ?
Are you sure it's still valid when calling update ?

mzimmers

Bingo...I wasn't creating it. I created the pointer but never invoked the c'tor from the parent. Now corrected:

EditDialog::EditDialog(DeviceModel *d, QModelIndex *qmi, Worker *pWorker, QWidget *parent) :
    QDialog(parent),
    ui(new Ui::EditDialog),
    m_d(d),
    m_qmi(qmi),
    m_worker(pWorker)
{   
    ui->setupUi(this);

       // create the model that holds the results of the AP scan.
    m_modelApScan = new ModelApScan();

Amazing the brain-dead mistakes one can make when distracted...thanks for the help.

SGaist

Side note (partly aesthetics), you can keep m_modelApScan in the initialiser list of your EditDialog class constructor.