Events
Introduction
Although many branches of Logic can be defined in Incari's Logic Editor, a branch will never be executed without being initiated by an Event. These Events define when, and under what conditions, functionality should be triggered. In both Incari and computer science in general, event systems define a relationship between the fulfillment of criteria and the set of instructions to be performed once those criteria are met. They are made up of two parts: triggers and listeners.
Triggers can be thought of as being like announcements. A real-world example of a trigger is a school teacher announcing that an exam's time limit has been reached. The other staff members and students are listeners in this case. The Event of the teacher's announcement prompts the students to put down their pencils, and staff members to begin collecting exam papers.
Events in Incari can be directly triggered by the user's input, as is the case with Keyboard and Mouse Events, or triggered automatically when something happens relating to an Object, Variable, Scene, or Screen. One of the most powerful aspects of Incari's Events is that you can even define your own custom triggers and listeners, to establish the criteria under which one part of your Logic causes the execution of others.
Subscribing and Unsubscribing
Most Event Nodes have an additional Subscribe input Pulse and some have an Event ID output Socket.
Subscribe is used to start listening to an Event when it is triggered by some arbitrary Node chosen by the user. This does not apply to Event Nodes that subscribe on initialization.
Once an Event is subscribed to, it can be unsubscribed from. This requires the Event's ID. If you recall, all items in Incari have a unique ID. In this case, an Event ID is a unique ID to a specific Event. This can be attached to the Unsubscribe Node, thus ending a connection to the Event. For Nodes with a Subscribe input, this can create a loop of subscribing and unsubscribing. Events that are subscribed to on initialization can only be unsubscribed from once.
External Links
What is event programming? on Musing Mortoray.
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