I have defined qml slot like this :
You are wrong. It is not slot definion, it's
(the adding of QML handler for signal
value_changed of object
That's why you code works. But in this line :
You are trying to connect existing signal
value_changed to inexisting
(obviously, it exists in your code, but not in
rootObject of view).
That's why you got warning.
You tried to connect signal
twice, but only
one method was successful, so
code worked well.