On<property name>Changed: undefined property

manuelsch

Hi,

corresponding to "the documentation":http://doc.qt.nokia.com/4.7-snapshot/qmlevents.html, on can catch changes of properties using the <property_name>Changed signal

I tried to implement this for the collection property of this object:
@import QtQuick 1.1
import "lib/json/json2.js" as Json

ListModel {
id: mongoQuery

property MongoCollection collection
property variant query
property variant sort
property int limit: -1
property int skip: 0
property bool snapshot: false
property bool $returnKey: false
property int $maxScan: -1
property variant $min
property variant $max
property bool $showDiskLoc: false
property variant $hin-t

function update() {
    clear()

    var cursor = collection.find(query)
    console.log( Json.JSON.stringify(query) )

    if ($returnKey)
        cursor = cursor._addSpecial("$returnKey", $returnKey)
    if (snapshot)
        cursor = cursor.snapshot()
    if ($min)
        cursor = cursor._addSpecial("$min", $min)
    if ($max)
        cursor = cursor._addSpecial("$max", $max)
    if ($showDiskLoc)
        cursor = cursor._addSpecial("$showDiskLoc", true)
    if ($hint)
        cursor = cursor._addSpecial("$hint", $hint)

    if (sort)
        cursor = cursor.sort(sort)
    if (skip>-1)
        cursor = cursor.skip(skip)
    if (limit>-1)
        cursor = cursor.limit(limit)

    while(cursor.hasNext)
        append(cursor.next())
}

onCollectionChanged: collection.refreshed.connect(update)

}
@

But I'm getting this error:
@file:///home/manuel/lib/QtMongo/QtMongo/MongoQuery.qml:50:5: ListModel: undefined property 'onCollectionChanged'
onCollectionChanged: collection.refreshed.connect(update)@

Is there anything I did not get?

thisisbhaskar

I don't think you will automatically get signal. You should define them and fire signal at appropriate places ( when you think property has changed ). In QML, everytime a property is changed, they must have been firing a signal with "propertyChanged" name. May be slot is automatically defined. I mean "onPropertyChanged" is automatically defined for you by the framework.

manuelsch

bq. I don’t think you will automatically get signal.

Well, have a look at the onXChanged example in the documentation I posted^^.
As far as I understand this, this slot will automatically be called.

thisisbhaskar

What you said is true..

@http://doc.qt.nokia.com/4.7/qml-extending-types.html
Property change signals

Adding a property to an item automatically adds a value changed signal handler to the item. To connect to this signal, use a signal handler named with the on<Property>Changed syntax, using upper case for the first letter of the property name.@

Its interesting. I suppose that MongoCollection is userdefined type. How can QML know when to raise a signal when you change some internal state of you type. When do you want qml to raise a signal for you???

manuelsch

Yes, it is a user defined QML type (not using C++ magic).

It should be raised after a call like this:
@mongoQuery.collection = myCollection@

mbrasser

Hi,

This might be because ListModel uses a custom parser -- does the following work for you?

@
Item {
property MongoCollection collection
onCollectionChanged: console.log("changed")
}
@

If so, I'd suggest logging a bug (something along the lines of "on<Property>Changed syntax doesn't work inside ListModel"), and seeing if you work around this in the mean time (maybe using a wrapper object and placing the property there if that is applicable in your case?)

Regards,
Michael

manuelsch

Hi Michael,

thanks, it works fine with the 'Item', so I created a "bug report":http://bugreports.qt.nokia.com/browse/QTBUG-19763