QStandardPaths not available in QML?

SGaist · wrote on 8 Dec 2015, 22:04

Hi,

You can create a small QObject derived class that will return the values you're interested in using Q_INVOKABLE functions.

xargs1 · 8 Dec 2015, 23:41

You don't have to write a plugin. As SGaist said, just write a simple QObject-derived class. It can be a single .h file and a call to qmlRegisterType in main.cpp.

? Offline · 12 Aug 2015, 23:42

@xargs1

Hey I did it! (and it didn't hurt too much...)

Am I doing it right ;-) And am I correct in thinking that I can't generalize this (e.g. have a "getPath(int pathType)? I tried passing in an int as an index to the enum: enum QStandardPaths::StandardLocation but that threw a type error.

#ifndef UTILITYRP
#define UTILITYRP

#include <QObject>
#include <QStandardPaths>

class UtilityRP : public QObject
{
    Q_OBJECT

public:
     Q_INVOKABLE QStringList getDesktopLocation() {

        return QStandardPaths::standardLocations(QStandardPaths::DesktopLocation);
    }
};

#endif // UTILITYRP

SGaist · 9 Dec 2015, 00:33

You can create a Q_ENUM and use it as parameter to your function. You can make it match the values you need from QStandardPaths so there's no translation needed just a cast.

? Offline · S SGaist 8 Dec 2015, 23:45

@SGaist

thanks! got that to work (assuming I am doing the cast correctly with static_cast<QStandardPaths::StandardLocation>(location);).

#ifndef UTILITYRP
#define UTILITYRP

#include <QObject>
#include <QStandardPaths>

class UtilityRP : public QObject
{
    Q_OBJECT

public:
    Q_INVOKABLE QStringList getPath(int location) {
        QStandardPaths::StandardLocation loc = static_cast<QStandardPaths::StandardLocation>(location);
        return QStandardPaths::standardLocations(loc);
    }
};

#endif // UTILITYRP

SGaist · 9 Dec 2015, 22:54

In this case, using an int is not clean. Your QML code won't make any sense (i.e. what is location 1 ?). You should really take the time to implement an enum for that. So that if any off the enum value changes, you won't have to update that part of your code and it will make it easier to read.

? Offline · S SGaist 9 Dec 2015, 22:24

@SGaist

Thanks. Yes, I realize using an arbitrary int kind of defeats the purpose of using an enum but I couldn't figure out how to do it on the QML side – the docs ( enumeration QML Basic Type ) are not very clear, nor how to expose the QStandardPaths:: StandardLocation to the QML.

SGaist · 11 Dec 2015, 04:35

That's the QML doc, you should do it from C++. Add an enum to your class that maps the StandardLocation values to your own and declare it as a Q_ENUM.

? Offline · S SGaist 9 Dec 2015, 23:00

@SGaist

Sorry, not following. Can you point me to an example that does that?

SGaist · 11 Dec 2015, 23:08

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QStandardPaths>
#include <QQmlComponent>

class UtilityRPAttachedEnums : public QObject
{
    Q_OBJECT
public:
    enum StandardLocation {
        DesktopLocation       = QStandardPaths::DesktopLocation,
        DocumentsLocation     = QStandardPaths::DocumentsLocation,
        FontsLocation         = QStandardPaths::FontsLocation,
        ApplicationsLocation  = QStandardPaths::ApplicationsLocation,
        MusicLocation         = QStandardPaths::MusicLocation,
        MoviesLocation        = QStandardPaths::MoviesLocation,
        PicturesLocation      = QStandardPaths::PicturesLocation,
        TempLocation          = QStandardPaths::TempLocation,
        HomeLocation          = QStandardPaths::HomeLocation,
        DataLocation          = QStandardPaths::DataLocation,
        CacheLocation         = QStandardPaths::CacheLocation,
        GenericCacheLocation  = QStandardPaths::GenericCacheLocation,
        GenericDataLocation   = QStandardPaths::GenericDataLocation,
        RuntimeLocation       = QStandardPaths::RuntimeLocation,
        ConfigLocation        = QStandardPaths::ConfigLocation,
        GenericConfigLocation = QStandardPaths::GenericConfigLocation,
        DownloadLocation      = QStandardPaths::DownloadLocation,
    };
    Q_ENUMS(StandardLocation)

public:
    UtilityRPAttachedEnums(QObject *parent)
        : QObject(parent)
    {}
    Q_INVOKABLE QStringList getPath(StandardLocation location) {
        QStandardPaths::StandardLocation loc = static_cast<QStandardPaths::StandardLocation>(location);
        return QStandardPaths::standardLocations(loc);
    }
};

class UtilityRP : public QObject
{
    Q_OBJECT
public:
    static UtilityRPAttachedEnums *qmlAttachedProperties(QObject *object)
    {
        return new UtilityRPAttachedEnums(object);
    }
};

QML_DECLARE_TYPEINFO(UtilityRP, QML_HAS_ATTACHED_PROPERTIES)

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    qmlRegisterUncreatableType<UtilityRP>("org.test.qmlcomponents", 1, 0, "UtilityRP", "Static");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

#include "main.moc"

main.qml

import QtQuick 2.3
import QtQuick.Controls 1.2

import org.test.qmlcomponents 1.0

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    menuBar: MenuBar {
        Menu {
            title: qsTr("File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: console.log("Open action triggered");
            }
            MenuItem {
                text: qsTr("Exit")
                onTriggered: Qt.quit();
            }
        }
    }

    MouseArea {
        id: mouseArea
        anchors.fill: parent
        Label {
            id: label
            text: qsTr("Click me")
            anchors.centerIn: parent
        }

        onClicked: {
            label.text = UtilityRP.getPath(UtilityRP.DesktopLocation);
        }
    }
}