Qt Quick returning objects from roles - qt

Question

I'm trying to get a role to return an object. I'm running into undefined errors when I try to access display.blockNumber and display.time
here's my code
blockdisplay.h:
#ifndef BLOCKDISPLAY_H
#define BLOCKDISPLAY_H
#include <QMetaType>
class BlockDisplay
{
public:
BlockDisplay();
BlockDisplay(int blocknum, long time);
BlockDisplay(const BlockDisplay &other);
~BlockDisplay();
int blockNumber() const;
long time() const;
private:
int m_blocknumber;
long m_time;
};
Q_DECLARE_METATYPE(BlockDisplay)
#endif // BLOCKDISPLAY_H
blockdisplay.cpp:
#include "blockdisplay.h"
BlockDisplay::BlockDisplay() {
}
BlockDisplay::BlockDisplay(int blocknum, long time) {
this->m_blocknumber = blocknum;
this->m_time = time;
}
BlockDisplay::BlockDisplay(const BlockDisplay &other) {
this->m_blocknumber = other.blockNumber();
this->m_time = other.time();
}
BlockDisplay::~BlockDisplay() {
}
int BlockDisplay::blockNumber() const {
return this->m_blocknumber;
}
long BlockDisplay::time() const {
return this->m_time;
}
modelclass.h:
#ifndef MODELCLASS_H
#define MODELCLASS_H
#include <QObject>
#include <QAbstractListModel>
#include <QStringListModel>
#include <blockchain.h>
class ModelClass : public QAbstractListModel
{
Q_OBJECT
Q_PROPERTY(qint32 blockheight READ blockheight)
protected:
Blockchain bc{};
int first;
public:
ModelClass();
qint32 blockheight();
void init();
int rowCount(const QModelIndex &parent = QModelIndex()) const;
QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
};
#endif // MODELCLASS_H
modelclass.cpp:
#include "modelclass.h"
#include <string.h>
#include <qdebug>
#include "blockdisplay.h"
using namespace std;
ModelClass::ModelClass()
{
}
void ModelClass::init() {
bc.init();
if ( !bc.Valid() )
qDebug() << "invalid";
else {
bc.SeekToFirst();
bc.Next();
if ( !bc.Valid() )
qDebug() << "invalid";
else
first = bc.GetCurrentBlock().signedhead().head().num();
}
//setProperty("blockheight",bc.GetBlockHeight());
}
qint32 ModelClass::blockheight() {
return bc.GetBlockHeight();
}
int ModelClass::rowCount(const QModelIndex &parent) const {
//qInfo() << " 0test " << bc.GetBlockHeight();
return bc.GetBlockHeight() - first;
}
QVariant ModelClass::data(const QModelIndex & index, int role) const {
qInfo() << " 1test " << index;
int row = bc.GetBlockHeight() - index.row();// + 1 + first;
if (index.isValid()) {
bc.Seek(row);
if (bc.Valid()) {
if (role == Qt::DisplayRole) {
int blocknum = bc.GetCurrentBlock().signedhead().head().num();
long timestamp = bc.GetCurrentBlock().signedhead().head().timestamp();
BlockDisplay dsply{blocknum, timestamp};
QVariant var = QVariant::fromValue(dsply);
return var;
}
}
}
return QVariant();
}
snippet from block.qml:
Component {
id: gridComp
Row {
Text {
text: display.blockNumber + " "
MouseArea {
anchors.fill: parent
onClicked: {
list.currentIndex = index;
ld.setSource("detail.qml")
}
}
}
Text {
text: display.time + " "
}
}
}

Answer 1

I think Q_DECLARE_METATYPE(BlockDisplay) is not enough. If you want to use its attributes in QML you have to use the Q_PROPERTY macro to create properties, just like you did for ModelClass. You may also have to call qRegisterMetaType
Adding a Q_DECLARE_METATYPE() makes the type known to all template based functions, including QVariant. Note that if you intend to use the type in queued signal and slot connections or in QObject's property system, you also have to call qRegisterMetaType() since the names are resolved at runtime.