Qt import library - creating a QML function

[teh_raab]

Hi All,

Im probably being really dumb and staring right at the issue but can't see the solution.. I've written an import library that we use for various Qt 4.8 QML applications. I have various objects that i can instantiate inside QML without any problem e.g.



Logger {
id: write;
name: "Main.qml";
Component.onCompleted: {
log("log started");
}
}


and as expected, have access to this "Logger" components "log" method e.g.



MouseArea {
anchors.fill: parent;
onClicked: {
write.log("Mouse area clicked)
console.log(convert.time_ms_to_sec(-1));
console.log(convert.time_ms_to_sec(15000));
}
}


This all works fine. My problem is that i now want to create some global functions inside my import library that can be called from anywhere without having to instantiate an object in every QML file. For example, i made a test function that converts milliseconds to seconds, but in order to use it i have to declare my "Conversion" object in each QML file, like..



Conversion {
id: convert;
}

MouseArea {
anchors.fill: parent;
onClicked: {
console.log(convert.time_ms_to_sec(15000));
}
}


Is there a way of doing this without having to declare the "Conversion {}"?!? I want to be able to simply call convert.time_ms_to_sec(<val>) in any script that has my import.

Thanks in advanced,

Raab.

[wysota]

You can make your plugin provide attached properties to objects or you can make it expose a global object using QQmlExtensionPlugin::initializeEngine() (or QDeclarativeExtensionPlugin::initializeEngine() if using Qt4). The latter would work similar to Math or Array objects in JavaScript.

[teh_raab]

Thanks :D QDeclarativeExtensionPlugin sounds exactly like what i'm after. I'll give it a bash.

[teh_raab]

So i had another look at the code (had to run after i sent previous reply so only just got back to looking at it).. I was already using the QDeclarativeExtensionPlugin. I just don't seem to be able to pin down the syntax. Here is what i have so far.

qmldir


plugin testplugin lib


testplugin.pro


TEMPLATE = lib
CONFIG += qt plugin
QT += declarative

DESTDIR = lib
OBJECTS_DIR = tmp
MOC_DIR = tmp

HEADERS += conversions.h \
testplugin.h

SOURCES += conversions.cpp \
testplugin.cpp


conversions.h


#ifndef CONVERSIONS_H
#define CONVERSIONS_H

#include <QDeclarativeItem>

class Conversions : public QDeclarativeItem
{
Q_OBJECT

public:
Conversions(QDeclarativeItem *parent = 0);

Q_INVOKABLE int time_ms_to_sec(int val);
};
#endif


testplugin.h


#ifndef TESTPLUGIN_H
#define TESTPLUGIN_H

#include <QDeclarativeExtensionPlugin>

class TestPlugin : public QDeclarativeExtensionPlugin
{
Q_OBJECT
public:
void registerTypes(const char *uri);
};
#endif


conversions.cpp


#include "conversions.h"

Conversions::Conversions(QDeclarativeItem *parent)
: QDeclarativeItem(parent)
{
// need to disable this flag to draw inside a QDeclarativeItem
setFlag(QGraphicsItem::ItemHasNoContents, false);
}


int Conversions::time_ms_to_sec(int val = -1) {
if(val == -1) {
return -1;
}
else {
return (val / 1000);
}
}



testplugin.cpp


#include "testplugin.h"
#include "conversions.h"
#include <qdeclarative.h>

void TestPlugin::registerTypes(const char *uri)
{
qmlRegisterType<Conversions>(uri, 1, 0, "Conversions");
}

Q_EXPORT_PLUGIN2(testplugin, TestPlugin);



And here is the QML -> I run this QML directly from QtCreater viewer. I have placed comments on line that is failing which shows what im trying to achieve.

Main.qml


import QtQuick 1.0
import TestPlugin 1.0

Item {
width: 100; height: 100

Conversions {
id: convv
Component.onCompleted: {
console.log("Test 1: " + convv.time_ms_to_sec(1000)); //Works ok
console.log("Test 2: " + time_ms_to_sec(2000)); //Works ok
}
}

MouseArea {
anchors.fill: parent;
onClicked: {
console.log("Test 3: " + convv.time_ms_to_sec(3000)); //Works ok
console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
}
}
}



My final goal being..

Main.qml


import QtQuick 1.0
import TestPlugin 1.0

Item {
width: 100; height: 100

MouseArea {
anchors.fill: parent;
onClicked: {
console.log("Test 4: " + Conversions.time_ms_to_sec(4000)); //DOES NOT WORK
}
}
}


I have seen references to "setContextProperty" but not sure if this is required for what im after, or if so how to use it.

Thanks again,

Rob.

[wysota]

Hmm... I even told you what function you were to reimplement :)


class Conversions : public QObject {
Q_OBJECT
public:
Conversions(QObject *parent = 0) : QObject(parent) {}
public slots:
int time_ms_to_sec(int val = -1) {
return val == -1 ? -1 : (val / 1000);
}
};

void TestPlugin::initializeEngine(QDeclarativeEngine *engine, const char *url) {
engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));
}

[teh_raab]

You Sir, are a legend :) It was pretty much what i had but could not work out the issue..

I had to change



engine->rootContext()->setContextProperty("Conversions", new Conversions(engine));


to be..



engine->rootContext()->setContextProperty("_conversions", new Conversions(engine));


I could then call from QML -> "_conversions.time_ms_to_sec(4000)". Im assuming thats because i already have "Conversions" as a registered type ("qmlRegisterType<Conversions>(uri, 1, 0, "Conversions");")!

Thanks once again.

[wysota]

The question is why you registered "Conversions". What is the point of doing that? How does your "Conversions" type differ from "Conversion"?

[teh_raab]

It shouldnt. That was just the original implementation that i wanted kept in until i got the above working. It has since been removed.