[Interest] Qml Loader initial property setter

[Sina Dogru]

>
> It's sad that the imperative setSource() function can set those property
> and the declarative way is not.
>

It would also be great but to make something a property instead of a
function where it is much easier, then there should be a public and
QMetaType known type.Thats why seems like hard to make it possible.

2016-04-04 16:31 GMT+03:00 Jérôme Godbout <jerome at bodycad.com>:

> Thanks for pointing this out, but I was aware of that. Sometime a default
> value is impossible (null) making bad behavior or bad binding, primitive
> type can always have default value that make sense that way but complex
> object don't.
> It's sad that the imperative setSource() function can set those property
> and the declarative way is not.
>
> On Sun, Apr 3, 2016 at 11:10 AM, ekke <ekke at ekkes-corner.org> wrote:
>
>> if you want to refer to a property as 'model.i' and there are situations
>> where 'model' doesn't exist always,
>> it's easy to avoid error messages:
>>
>> model? model.i : 42
>>
>> this way you can set a default value while model is null
>> (haven't tried this yet with Qt 5.6 but I'm doing it this way in
>> BlackBerry 10 Cascades)
>>
>> ekke
>>
>> Am 01.04.16 um 16:05 schrieb Jérôme Godbout:
>>
>> Yes, but the binding loaded object internal binding are printing error,
>> since the object is created without the input, then the external binding
>> are created. They will get eventually correct, but the console will be
>> filled with error message and I try to avoid that at all cost. Here's a
>> simple example that will complain about unable to access i and j of
>> undefined / assign undefined to width and height (this example is a bit
>> stupid but just a demo to show the problems with more complex model and
>> object):
>>
>> // MyComponent.qml
>> Item
>> {
>>  property var model
>>  width: model.i
>>  height: model.j
>> }
>>
>> // Main.qml
>> MyModel
>> {
>>   id: myModel_
>>   property int i: 24
>>   property int j: 12
>> }
>>
>> Loader
>> {
>>   id: loader_
>>   source: "MyComponent.qml"
>> }
>>
>> Binding
>> {
>>   target: loader_.item
>>   property: 'model'
>>   value: myModel_
>>   when: loader_.status == Loader.Ready
>> }
>>
>> What I would like is the Loader call QQmlComponent::beginCreate(), then
>> having a hook to init some property then the Loader can finish the
>> component QQmlComponent::completeCreate(). This way I was able to make it
>> work, but having a custom component for that is a bit annoying.
>>
>> Loader
>> {
>>   source: "MyComponent.qml"
>>   onInitProperty:  // signal emit with component object returned by
>> beginCreate(),
>>   {
>>     object.model = Qt.binding(function(){ return myModel_; });
>>     ...
>>   }
>> }
>>
>> That seem clean and would avoid the problems to have object into bad
>> state for a brief moment.
>>
>> Jerome
>>
>> On Fri, Apr 1, 2016 at 12:04 AM, Shantanu Tushar <shaan7in at gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> Have you tried using the QML Binding Type?
>>> <http://doc.qt.io/qt-5/qml-qtqml-binding.html>
>>> http://doc.qt.io/qt-5/qml-qtqml-binding.html
>>>
>>> On Thu, Mar 24, 2016 at 11:11 PM, Jérôme Godbout < <jerome at bodycad.com>
>>> jerome at bodycad.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> I was wondering if I am the only one who found the initial property of
>>>> a source based Loader Item a bit annoying. inline sourceComponent with
>>>> Component {} declaration are well ok on the other hand. I'm explaining
>>>> myself, when using a loader you have 2 choice to set the initial binding on
>>>> created item:
>>>>
>>>> 1- On item changed set the binding
>>>>
>>>> *Loader*
>>>> *{*
>>>> *  source: externalObj.getSrc() // return something like "myItem.qml"*
>>>> *  onItemChanged:*
>>>> *  {*
>>>> *    if(!item) return;*
>>>> *    item.myprop = Qt.binding(function(){ return myExternalProperty; })*
>>>> *  }*
>>>> *}*
>>>>
>>>> 2- use the setSource() function instead of the source directly
>>>>
>>>> *Loader*
>>>> *{*
>>>> *  property url myDummySrc: externalObj.getSrc()*
>>>> *  onMyDummySrcChanged:*
>>>> *  {*
>>>> *     setSource(myDummySrc, { 'myprop': Qt.binding(function(){ return
>>>> myExternalProperty; }) });*
>>>> *  }*
>>>> *}*
>>>>
>>>> This is rather annoying and ugly. Number 1 is also having the problem
>>>> where *myItem.qml* must be able to handle *myprop *to have a default
>>>> value or being empty without output a lots of console error. Number 2 work
>>>> well and is the solution I find myself writing often. I was wondering if a
>>>> Loader that support a dictionary of initial property when source changed
>>>> would be nice:
>>>>
>>>> *Loader*
>>>> *{*
>>>> *  source: externalObj.getSrc()*
>>>> *  initialProperties: { 'myprop': Qt.binding(function(){ return
>>>> myExternalProperty; })  }*
>>>> *}*
>>>>
>>>> What do you think?
>>>> Jerome
>>>>
>>>> _______________________________________________
>>>> Interest mailing list
>>>> Interest at qt-project.org
>>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>>
>>>>
>>>
>>>
>>> --
>>> Shantanu Tushar    (UTC +0530)
>>> shantanu.io
>>>
>>
>>
>>
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