Understanding argument `const char * uri` of `qmlRegisterType`

From: http://qt-project.org/doc/qt-4.8/dec...r1-basics.html

Code:

---

import Charts 1.0
 import QtQuick 1.0
 
 Item {
     width: 300; height: 200
 
     PieChart {
         id: aPieChart
         anchors.centerIn: parent
         width: 100; height: 100
         name: "A simple pie chart"
         color: "red"
     }
 
     Text {
         anchors { bottom: parent.bottom; horizontalCenter: parent.horizontalCenter; bottomMargin: 20 }
         text: aPieChart.name
     }
 }

---

Code:

---

#include "piechart.h"
 #include <qdeclarative.h>
 #include <QDeclarativeView>
 #include <QApplication>
 
 int main(int argc, char *argv[])
 {
     QApplication app (argc, argv);
 
     qmlRegisterType<PieChart> ("Charts", 1, 0, "PieChart");
 
     QDeclarativeView view;
     view.setSource (QUrl::fromLocalFile("app.qml"));
     view.show ();
     return app.exec();
 }

---

Question:
The QML file contains:
import Charts 1.0

That must be some special module for PieCharts drawing.
How do I know what module should be imported for drawing "lines", "circles", etc?

and the main.cpp contains:
qmlRegisterType<PieChart> ("Charts", 1, 0, "PieChart");

From: http://qt-project.org/doc/qt-5.0/qtq...mlRegisterType

Quote:

---

This template function registers the C++ type in the QML system with the name qmlName, in the library imported from uri having the version number composed from versionMajor and versionMinor.

---

What is it about 'uri'?
I couldn't understand that argument, Please explain.
For example instead of Piechart, if I draw a line, then what would be uri argument?

The uri is the module identifier, the thing you write after import in QML.

E.g. the uri for QtQuick itself is "QtQuick", the uri for that Chart library/module seems to be "Chart".

As you can see it is very often only a single word, but it could also be things like "com.ourcompany.OurComponents" and then the respective import would be

Code:

---

import com.ourcompany.OurComponents 1.0

---

where 1.0 is the two numbers given at the type register call.

So if we look at

Code:

---

qmlRegisterType<PieChart> ("Charts", 1, 0, "PieChart");

---

we can determine the arguments as
"Charts": name of the module
"PieChart": name of the element
1: major version number
0: minor version number

Cheers,
_

Thanks for your response, but

Quote:

---

Originally Posted by anda_skoa

The uri is the module identifier, the thing you write after import in QML.
E.g. the uri for QtQuick itself is "QtQuick", the uri for that Chart library/module seems to be "Chart".

---

For example, If I have to draw a "line" through "QPainter", what would be the module's name for uri argument?

It;s up to you -- how you name it using qmlRegisterType it's how it will have to appear in Qml's import section.
So, for instance, you can have several classes which represent business logic, so you can give uri as "business", UI stuff you can put into "ui" uri.
So, basically, it's like "libraries" in C++ terms.

Quote:

---

Originally Posted by spirit

It;s up to you -- how you name it using qmlRegisterType it's how it will appear in Qml's import section.
So, for instance, you can have several classes which represent business logic, so you can give uri as "business", UI stuff you can put into "ui" uri.
So, basically, it's like "libraries" in C++ terms.

---

Thanks.
I see now, you mean to say that "whatever" name we choose to register with qmlRegisterType, same will be imported in QtQuick.

Quote:

---

Originally Posted by Anisha Kaul

I see now, you mean to say that "whatever" name we choose to register with qmlRegisterType, same will be imported in QtQuick.

---

Yes. The first string is the name that appears after "import" the second string is the name of the element that can be used in QML.

Cheers,
_

Also if you are using Qt 5.0 + , do check out this link .

There has been lot of difference in QML between 4.8.x and 5.x . Its confusing sometimes as when you cant find classes you see on net. The examples are mostly of Qt 4.8.x on internet.