QML: List all object members/properties in console - qt

Question

Is there any way to list all object members/properties in QML & Qt 5.1?
Such as:
var obj=myQObject;
console.log(obj)
// expected output:
// obj { x:123..... }
This would be very helpful for debugging.

Answer 1

Straight javascript offers what you are looking for:
JSON.stringify(anything)
It works on QML items such as Rectangle, and it also works on most arbitrary objects!
Converting an object to a string

Answer 2

With meta objects you can debug all properties of any QML obj (i.e. QQuickItem).
You need some C++ to get the meta object of a QML component and get back property names and values as text in QML.
First you create a QMLDebugger class in C++ with a properties method:
QString QMLDebugger::properties(QQuickItem *item, bool linebreak)
{
const QMetaObject *meta = item->metaObject();
QHash<QString, QVariant> list;
for (int i = 0; i < meta->propertyCount(); i++)
{
QMetaProperty property = meta->property(i);
const char* name = property.name();
QVariant value = item->property(name);
list[name] = value;
}
QString out;
QHashIterator<QString, QVariant> i(list);
while (i.hasNext()) {
i.next();
if (!out.isEmpty())
{
out += ", ";
if (linebreak) out += "\n";
}
out.append(i.key());
out.append(": ");
out.append(i.value().toString());
}
return out;
}
This function can be static or instanceiable, doesn't matter. QML does not support exporting static methods from C++ to QML anyway. I use the header:
public:
Q_INVOKABLE static QString properties(QQuickItem *item, bool linebreak = true);
Now you export the class to QML. In you main.cpp add
#include "qmldebugger.h"
and
qmlRegisterType<QMLDebugger>("MyDemoLibrary", 1, 0, "QMLDebugger");
In your QML file import you new library, create an instance of QMLDebugger and start happy debugging:
import QtQuick 2.0
import MyDemoLibrary 1.0
Rectangle {
id: mainRectangle
width: 360
height: 360
color: "silver"
Text {
id: textElement
color: "#d71f1f"
text: qsTr("Hello World")
font.bold: true
font.italic: true
font.underline: true
style: Text.Raised
horizontalAlignment: Text.AlignHCenter
font.pointSize: 16
anchors.top: parent.top
anchors.left: parent.left
anchors.right: parent.right
}
QMLDebugger {
id: qmlDebugger
}
Component.onCompleted: {
console.log("Debug mainRectangle:");
console.log(qmlDebugger.properties(mainRectangle));
console.log("Debug textElement:");
console.log(qmlDebugger.properties(textElement, false));
}
}
The full source code is available as a minimal Qt Creator project on: https://github.com/webmaster128/QMLDebugger

Answer 3

Just convert the QML/C++ component/object into JavaScript var object, and use the for-each syntax to list all the property:
function listProperty(item)
{
for (var p in item)
console.log(p + ": " + item[p]);
}
in your QML file, just call
onClicked:
{
listProperty(ItemID)
//or with this to list self properties
listProperty(this)
}

Answer 4

in case of any one wants to list only properties of an object, no signals nor slots you can use this
function listProperty(item)
{
for (var p in item)
{
if( typeof item[p] != "function" )
if(p != "objectName")
console.log(p + ":" + item[p]);
}
}

Answer 5

If you are not only interested in console-debugging, there is a program called GammaRay by KDAB (link) that lets you introspect and change all properties during the runtime of a QWidgets or QtQuick based program. Pretty neat!

Answer 6

I did not see a solution to iterate all properties yet. But maybe this helps you as a first step.
For every Quick Item you can print out the properties of Item:
import QtQuick 2.0
Rectangle {
width: 360
height: 360
function debugQuickItem(object) {
var properties = {
'activeFocus': object.activeFocus,
'activeFocusOnTab': object.activeFocusOnTab,
'anchors.alignWhenCentered': object.anchors.alignWhenCentered,
'anchors.baseline': object.anchors.baseline,
'anchors.baselineOffset': object.anchors.baselineOffset,
'anchors.bottom': object.anchors.bottom,
'anchors.bottomMargin': object.anchors.bottomMargin,
'anchors.centerIn': object.anchors.centerIn,
'anchors.fill': object.anchors.fill,
'anchors.horizontalCenter': object.anchors.horizontalCenter,
'anchors.horizontalCenterOffset': object.anchors.horizontalCenterOffset,
'anchors.left': object.anchors.left,
'anchors.leftMargin': object.anchors.leftMargin,
'anchors.margins': object.anchors.margins,
'anchors.right': object.anchors.right,
'anchors.rightMargin': object.anchors.rightMargin,
'anchors.top': object.anchors.top,
'anchors.topMargin': object.anchors.topMargin,
'anchors.verticalCenter': object.anchors.verticalCenter,
'anchors.verticalCenterOffset': object.anchors.verticalCenterOffset,
'antialiasing': object.antialiasing,
'baselineOffset': object.baselineOffset,
'children': object.children,
'childrenRect.height': object.childrenRect.height,
'childrenRect.width': object.childrenRect.width,
'childrenRect.x': object.childrenRect.x,
'childrenRect.y': object.childrenRect.y,
'clip': object.clip,
'data': object.data,
'enabled': object.enabled,
'focus': object.focus,
'height': object.height,
'implicitHeight': object.implicitHeight,
'implicitWidth': object.implicitWidth,
'layer.effect': object.layer.effect,
'layer.enabled': object.layer.enabled,
'layer.format': object.layer.format,
'layer.mipmap': object.layer.mipmap,
'layer.samplerName': object.layer.samplerName,
'layer.smooth': object.layer.smooth,
'layer.sourceRect': object.layer.sourceRect,
'layer.textureSize': object.layer.textureSize,
'layer.wrapMode': object.layer.wrapMode,
'opacity': object.opacity,
'parent': object.parent,
'resources': object.resources,
'rotation': object.rotation,
'scale': object.scale,
'smooth': object.smooth,
'state': object.state,
'states': object.states,
'transform': object.transform,
'transformOrigin': object.transformOrigin,
'transitions': object.transitions,
'visible': object.visible,
'visibleChildren': object.visibleChildren,
'width': object.width,
'x': object.x,
'y': object.y,
'z': object.z,
}
var out = "{ "
for (var key in properties)
{
out += "'" + key + "': " + properties[key] + ", "
}
out += "}"
return out;
}
Text {
id: textObject
anchors.centerIn: parent
text: "Hello World"
}
Component.onCompleted: console.log(debugQuickItem(textObject));
}
Output:
{ 'activeFocus': false, 'activeFocusOnTab': false, 'anchors.alignWhenCentered': true, 'anchors.baseline': QVariant(QQuickAnchorLine), 'anchors.baselineOffset': 0, 'anchors.bottom': QVariant(QQuickAnchorLine), 'anchors.bottomMargin': 0, 'anchors.centerIn': QQuickRectangle_QML_0(0x29857d0), 'anchors.fill': null, 'anchors.horizontalCenter': QVariant(QQuickAnchorLine), 'anchors.horizontalCenterOffset': 0, 'anchors.left': QVariant(QQuickAnchorLine), 'anchors.leftMargin': 0, 'anchors.margins': 0, 'anchors.right': QVariant(QQuickAnchorLine), 'anchors.rightMargin': 0, 'anchors.top': QVariant(QQuickAnchorLine), 'anchors.topMargin': 0, 'anchors.verticalCenter': QVariant(QQuickAnchorLine), 'anchors.verticalCenterOffset': 0, 'antialiasing': false, 'baselineOffset': 14, 'children': [object Object], 'childrenRect.height': 0, 'childrenRect.width': 0, 'childrenRect.x': 0, 'childrenRect.y': 0, 'clip': false, 'data': [object Object], 'enabled': true, 'focus': false, 'height': 17, 'implicitHeight': 17, 'implicitWidth': 80.5625, 'layer.effect': null, 'layer.enabled': false, 'layer.format': 6408, 'layer.mipmap': false, 'layer.samplerName': source, 'layer.smooth': false, 'layer.sourceRect': QRectF(0, 0, 0, 0), 'layer.textureSize': QSize(-1, -1), 'layer.wrapMode': 0, 'opacity': 1, 'parent': QQuickRectangle_QML_0(0x29857d0), 'resources': [object Object], 'rotation': 0, 'scale': 1, 'smooth': true, 'state': , 'states': [object Object], 'transform': [object Object], 'transformOrigin': 4, 'transitions': [object Object], 'visible': true, 'visibleChildren': [object Object], 'width': 80.5625, 'x': 139.71875, 'y': 171, 'z': 0, }