on<property name>Changed: undefined property
Hi,
corresponding to the documentation [doc.qt.nokia.com], 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?
6 replies
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.
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???
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
Hi Michael,
thanks, it works fine with the ‘Item’, so I created a bug report [bugreports.qt.nokia.com]
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