EWOL: Object message

@tableofcontents

Objectifs:

Understand base of e-signal Messaging system
Create extern message and receive Object message

Message system

esignal base his signal on landa functions

It permit to an object to generate some 'signals'

All signal are synchronous (asynchronous is not implemented yet)

Receive signals from other object

Button header :

	...
	public:
		esignal::Signal<> signalDown;
		esignal::Signal<> signalUp;
		...
		esignal::Signal<bool> signalValue;
	...

simple signal connection:

#include <ewol/object/Object.hpp>
#include <ewol/widget/Button.hpp>
namespace appl {
	class MyObj : public ewol::Object {
		private:
			ewol::widget::ButtonShared m_button;
			esignal::Connection m_connect;
		protected:
			//! @brief Constructor
			MyObj() {
				// nothing to do..
			}
			void init() {
				ewol::Object::init();
				m_button = ewol::widget::Button::create();
				if (m_button == nullptr) {
					APPL_ERROR("Can not create button...");
					return;
				}
				m_button->propertyToggle.set(true);
				// We connect signals here: (permanent connection)
				m_button->signalUp.connect(sharedFromThis(), &appl::MyObj::onCallbackUp);
				m_button->signalValue.connect(sharedFromThis(), &appl::MyObj::onCallbackValue);
			}
		public:
			//! @brief Destructor
			virtual ~MyObj() { }
			DECLARE_FACTORY(MyObj);
		private:
			void onCallbackUp() {
				APPL_INFO("button pressed: UP");
			}
			void onCallbackDown() {
				APPL_INFO("button pressed: DOWN");
			}
			void onCallbackValue(const bool& _value) {
				APPL_INFO("button value: " << _value);
				if (_value == true) {
					// We connect signals here: (removable connection)
					m_connect = m_button->signalDown.connect(this, &appl::MyObj::onCallbackDown);
				} else {
					// we disconnect the previous connection
					m_connect.disconnect();
				}
			}
	}
}

Note:

	The connection with SharedPtr are static. they keep in internal a WeakPtr to remove connection if the object is removed.

Note:

	The connection that return a esignal::Connection are volatil, if you don't keep the connection handle, the connection is automaticly removed.

Declare Signal:

source

#include <ewol/object/Object.hpp>
#include <ewol/widget/Button.hpp>
namespace appl {
	class MyObj : public ewol::Object {
		public:
			ewol::object::Signal<> signalEmpty;
			ewol::object::Signal<bool> signalBoolean;
			ewol::object::Signal<etk::String> signalString;
		protected:
			//! @brief Constructor
			MyObj() :
			  signalEmpty(this, "empty"),
			  signalBoolean(this, "boolean"),
			  signalString(this, "string") {
				// nothing to do..
			}
		public:
			//! @brief Destructor
			virtual ~MyObj() { }
			DECLARE_FACTORY(MyObj);
		private:
			void process() {
				signalEmpty.emit();
				signalBoolean.emit(false);
				signalString.emit("plop... plop");
			}
	}
}

Conclusion:

You will now able to reise signals between objects...

For more information see e-signal

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