events

Events are a way to communicate between systems. They are used to notify of changes and trigger callbacks associated with them. The event system in fresa is really simple, you just need to create an event object and subscribe functions to it.

event object

An event is defined by events::Event. It can have zero or some template parameters, which are the types that will be passed to the subscriber functions. Creating an event is as simple as to define it.

events::Event<> e;
events::Event<int, float> e;

add a callback

To add a function to an event you may call the method add() with a suitable function (must match the event template parameters).

events::Event<int, float> e;

//: with a lambda
e.add([](int i, float f) {
    log::info("event received: {} {}", i, f);
});

//: with a function
void callback(int i, float f) {
    log::info("event received: {} {}", i, f);
}
e.add(callback);

When adding a callback, the method will return an events::CallbackID handle, which can be stored to access the callback later (for example, to remove it).

events::CallbackID id = e.add([](){});

remove a callback

To remove a callback you may call the method remove() with the events::CallbackID handle.

events::Event<> e;
events::CallbackID id = e.add([](){});
e.remove(id);

You can remove all callbacks with the method reset().

e.reset();

publish an event

When an event is published, all callbacks are called with the event parameters. The publish() method takes the same parameters as the event template. Event callbacks are thread safe and there are no guarantees about the order in which they are called. If a callback is removed from the event, it will not be called when the event is published.

events::Event<int, float> e;
events::CallbackID id = e.add([](int i, float f) {
    log::info("event received: {} {}", i, f);
});
e.publish(1, 2.0f);

// >> event received: 1 2.0