Qt example (World Time Clock Plugin Example ) Notification Error :could not find the executable please specify one

[SoheilSabz]

Hi:

I need to learn more about using the ready and written widget into my new mainwindows or widgets, So I have reached to Custom Widget Plugin by this link descriptions and for example, I need to run this example :
World Time Clock Plugin Example
The file worldtimeclockplugin.pro is :

#! [0]
QT          += widgets uiplugin
#! [0]

QTDIR_build {
# This is only for the Qt build. Do not use externally. We mean it.
PLUGIN_TYPE = designer
PLUGIN_CLASS_NAME = WorldTimeClockPlugin
load(qt_plugin)
CONFIG += install_ok
} else {
# Public example:

TARGET      = $$qtLibraryTarget($$TARGET)
#! [1]
CONFIG     += plugin
TEMPLATE    = lib
#! [1]

target.path = $$[QT_INSTALL_PLUGINS]/designer
#target.path =/home/so/Qt/5.12.3/gcc_64/plugins/designer

INSTALLS += target

}

#! [2]
HEADERS     = worldtimeclock.h \
              worldtimeclockplugin.h
SOURCES     = worldtimeclock.cpp \
              worldtimeclockplugin.cpp
#! [2]

of Qt, but when i want to run it via relase mode i get The Could not find the executable please specify one notification :

So I found this instruction to solve this problem :

It should be compiled that the plugin is not an executable file, so qt
can't find a file that can be executed. The solution is: Solution

Only "build" does not "run", in general, in order not to pollute the
source code, a build folder will be created to store the compiled
code, and then used in the build folder.

Sudo make install

now i went to the release folder :

/home/so/Qt/Examples/Qt-5.12.3/designer/build-worldtimeclockplugin-Desktop_Qt_5_12_3_GCC_64bit2-Release/tras

and I do sudo make install, I get this output:

/home/so/Qt/5.12.3/gcc_64/bin/qmake -install qinstall -exe libworldtimeclockplugin.so /home/so/Qt/5.12.3/gcc_64/plugins/designer/libworldtimeclockplugin.so
strip --strip-unneeded /home/so/Qt/5.12.3/gcc_64/plugins/designer/libworldtimeclockplugin.so

It has created the libworldtimeclockplugin.so file and the folder is shown below:

but again I have the already notification.

What should I do? how can I solve this problem?

My stackoverflow question link is:

https://stackoverflow.com/questions/56788796/qt-example-world-time-clock-plugin-example-notification-error-could-not-find

[jsulm]

@SoheilSabz If you're creating a plug-in for designer then you need to copy the final plug-in library to the same location where other designer plug--ins are. Also, you have to use same Qt version which was used to build your version of designer.