Question about Component.onCompleted: signal handler

Ash V

Can you please tell me why the completed() signal is handled as Component.onCompleted()? I want to know about the Component. part.

I understand that completed() is a signal emitted by the Component object type of the QtQml module. But, I cannot understand why this signal is accessible in every QtQuick module object type as well.

import QtQuick
Item{
 Component.onCompleted:{
  console.log("Hello World")
 }
}

Bondrusiek

Component is a special type in the QtQml module that acts as a blueprint for creating objects in QML. Every QML object is implicitly part of a Component, even if you don't explicitly wrap it in a Component block. For example:

import QtQuick
Item {
 Component.onCompleted: {
  console.log("Hello World")
 }
}

Internally, QML treats this as if it is wrapped in a Component:

import QtQuick

Component {
Item {
 Component.onCompleted: {
  console.log("Hello World")
 }
}
}

You can analyze QQuickItem class and you will see that it inherits from QObject and QQmlParserStatus, hence it is possible to call Component.onCompleted() in Item objects.