ewol/doc/tutorial/010_ObjectModel.md

EWOL: Object model

@tableofcontents

Objectifs:

• Understand ewol basic ewol::Object
• Use ewol::Object correctly

Basis of the ewol::Object

An object in Ewol is a simple class: ewol::Object This object is the basis of all element in the ewol system. This is designed to manage many common things:

• Unique ID
• Name
• Parameters
• Signal generation
• Xml configuration
• Removing

Note:

Please do not compare with the gObject basic class...

Create an Object:

Creating an object is really simple:

	ewol::widget::ButtonShared tmpButon = ewol::widget::Button::create();
	APPL_INFO("We just create a button widget with unique ID=" << tmpButon->getId() << " name='" << tmpButon->propertyName.get() << "'");

Note:

	The widget is not stored in a ememory::SharedPtr<ewol::widget::Button> but in a ewol::widget::ButtonShared to simplify the using of the pointer.
	You have also: ememory::WeakPtr<ewol::widget::Button> = ewol::widget::ButtonWeak

Set the name of the object:

	tmpButon->propertyName.set("my widget name");
	APPL_INFO("We just create an Object with ID=" << tmpButon->getId() << " name='" << tmpButon->propertyName.get() << "'");

Remove an Object:

Simply use the function:

	tmpButon->destroy();

This function request his parrent to remove the ememory::SharedPtr it keep on it. And when all ememory::SharedPtr is removed the object will be really removed.

At his point we can think an object is alive all the time someone keep a reference on it, then when you are not a parrent of the object, do not keep a ememory::SharedPtr but a ememory::WeakPtr.

Note:

If some Object is not removed when you close the application, the system inform you with displaying all object alive.

Retrieve an Object:

In Ewol this is possible to get a object with his name.

Find a global Object (ouside an Object)

	#include <ewol/context/Context.hpp>
	
	ewol::ObjectShared tmpObject = ewol::getContext().getEObjectManager().getObjectNamed("obj Name");
	if (tmpObject == null) {
		APPL_ERROR("The Object does not exist");
	}

Find a global Object (inside an Object)

	ewol::ObjectShared tmpObject = getObjectNamed("obj Name");
	if (tmpObject == null) {
		APPL_ERROR("The Object does not exist");
	}

Find a sub-object

	ewol::ObjectShared tmpObject = getSubObjectNamed("obj Name");
	if (tmpObject == NULL) {
		APPL_ERROR("The Object does not exist");
	}

retriving your object type

It could be really interesting to retrive your own instance:

	ewol::ObjectShared tmpObject ...;
	
	appl::MyOwnObjectShared myObject = ememory::dynamicPointerCast<appl::MyOwnObject>(tmpObject);