On Sun, 27 Oct 2019 at 09:01, Maaza Mekuria <[email protected]> wrote:
>
> Thank you Etienne.  I did just what you suggested. But did not het anywhere.  
> I still get the same error message.
>
> My question did not get resolved and only for lack of information i can't 
> move forward with the upgrade.
> What i think has happened is that QGIS leadership has chosen to control the 
> access gates to "ousiders" who want to program in C++ and related functiions 
> in producing plugins by controlling how plugins are registered.
>
> It is a pity that I can't upgrade this plugin for lack of information.
>
> In the past i have donated money and willing to donate time and money.  Whay 
> is there so much secrecy on the basic C++ plugin initialization and registry? 
>  It does not make for a good and inclusive  policy.

There's no conspiracy here -- rather, c++ plugins have always been
horrible to build, deploy and debug (especially on Windows). Over time
the core project recognised this, realised it was a bad situation for
developers like yourself, and started encouraging people to completely
avoid using c++ plugins and move to Python wherever possible.

I strongly suspect that the reason no-one has answered your question
is just because no-one **knows** the answer! (I certainly don't -- I
saw your earlier thread, and the only advice I was able to offer at
the time was what Etienne had already suggested).

Nyall


>
> Thank for your help anyway.
>
>
> On Sun, Sep 15, 2019, 9:11 PM Etienne Trimaille <[email protected]> 
> wrote:
>>
>> Hi,
>>
>> I can't really answer your question but you should use 
>> https://qgis.org/api/classQgsMapLayerComboBox.html instead of creating your 
>> own combobox. (if possible).
>>
>> Etienne
>>
>> Le dim. 15 sept. 2019 à 10:11, Maaza Mekuria <[email protected]> a écrit :
>>>
>>> QGIS Layer List upgrade to V3 C++ plugin - Geographic Information Systems 
>>> Stack Exchange <style>body,.top-bar{margin-top:1.9em}</style>
>>>
>>> I was upgrading a c++ plugin that I had used in the past and almost 
>>> eliminated all the the usual compiler errors due to version changes 
>>> according for the current version (3.6). The plugin used to collect current 
>>> map canvas layers in a combo list box for selection. I am getting two 
>>> errors that I can't figure out what to do with. This code compiled without 
>>> problem pre-2.0.
>>>
>>> The first happens to be about QGSMapLayer that can't be instantiated 
>>> because it is turned as an abstract class and I am getting an error 
>>> [Severity Code Description Project File Line Source Suppression State Error 
>>> C2259 'QgsMapLayer': cannot instantiate abstract class tarjan_sccplugin 
>>> C:\OSGeo4W64\apps\Qt5\include\QtCore\qlist.h 214 Build ]
>>>
>>> This is portion of the code generating the error.  Where cmbNetSourceLayer 
>>> is a combo-box .
>>>
>>> void tarjan_sccGui::populateLayers( QString const& url ) { 
>>> cmbNetSourceLayer->clear();
>>>
>>> QString layerName; QString layerType;
>>>
>>> // fill list of layers
>>> QMap<QString, QgsMapLayer*> mapLayers = QgsProject::instance()->mapLayers();
>>> QMap<QString, QgsMapLayer*>::iterator layer_it = mapLayers.begin();
>>>
>>> for (; layer_it != mapLayers.end(); ++layer_it)
>>> {
>>>     QgsVectorLayer* vl = dynamic_cast<QgsVectorLayer*>(layer_it.value());
>>>     if (!vl)
>>>         continue;
>>>     else
>>>
>>>      cmbNetSourceLayer->addItem(vl->name() );
>>> }
>>>
>>> The second error appears to be in explicit declaration for the plugin. 
>>> Something has changed in how the plugins are initiated. [Severity Code 
>>> Description Project File Line Source Suppression State Error (active) 
>>> invalid explicit instantiation declaration tarjan_sccplugin 
>>> d:\GIS\v3\Quantum-GIS\src\core\qgsoptionalexpression.h 82 IntelliSense ]
>>>
>>> No idea what must be done to overcome this error.  The cited module appears 
>>> to be an optional data module.
>>>
>>>
>>> Any help is appreciated.
>>>
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