Event - is a single file Lua module for the Defold game engine. It provides a simple and efficient way to manage events and callbacks in your game.
- Event Management: Create, subscribe, unsubscribe, and trigger events.
- Cross-Context: You can subscribe to events from different scripts.
- Callback Management: Attach callbacks to events with optional data.
- Global Events: Create and subscribe global events that can be triggered from anywhere in your game.
- Logging: Set a logger to log event activities.
- Memory Allocations Tracker: Detects if an event callback causes a huge memory allocations.
Open your game.project
file and add the following line to the dependencies field under the project section:
https://github.com/Insality/defold-event/archive/refs/tags/2.zip
Note: The library size is calculated based on the build report per platform
Platform | Library Size |
---|---|
HTML5 | 1.96 KB |
Desktop / Mobile | 3.35 KB |
The project already includes the Lua Script Instance library. If Lua Script Instance is listed in your project's dependencies, remove it to prevent duplication.
Enabling in game.project
To monitor memory allocations for event callbacks, add to your game.project
:
[event]
memory_threshold_warning = 50
memory_threshold_warning
: Threshold in kilobytes for logging warnings about memory allocations.0
disables tracking.
Release Build Behavior
Memory allocation tracking is turned off in release builds, regardless of the game.project
settings.
event.set_logger(logger)
event.create(callback, [callback_context])
event:subscribe(callback, [callback_context])
event:unsubscribe(callback, [callback_context])
event:is_subscribed(callback, [callback_context])
event:trigger(...)
event:is_empty()
event:clear()
events.subscribe(name, callback, [callback_context])
events.unsubscribe(name, callback, [callback_context])
events.is_subscribed(name, callback, [callback_context])
events.trigger(name, ...)
events.clear(name)
events.clear_all()
To start using the Event module in your project, you first need to import it. This can be done with the following line of code:
local event = require("event.event")
Customize the logging mechanism used by Event module. You can use Defold Log library or provide a custom logger.
event.set_logger([logger_instance])
-
Parameters:
logger_instance
(optional): A logger object that follows the specified logging interface, including methods fortrace
,debug
,info
,warn
,error
. Passnil
to remove the default logger.
-
Usage Example:
Using the Defold Log module:
-- Use defold-log module
local log = require("log.log")
local event = require("event.event")
event.set_logger(log.get_logger("event"))
Creating a custom user logger:
-- Create a custom logger
local logger = {
trace = function(_, message, context) end,
debug = function(_, message, context) end,
info = function(_, message, context) end,
warn = function(_, message, context) end,
error = function(_, message, context) end
}
event.set_logger(logger)
Remove the default logger:
event.set_logger(nil)
event.create(callback, [callback_context])
Generate a new event instance. This instance can then be used to subscribe to and trigger events.
-
Parameters:
callback
: The function to be called when the event is triggered.callback_context
(optional): The first parameter to be passed to the callback function.
-
Return Value: A new event instance.
-
Usage Example:
local callback = function(self) print("clicked!") end
local on_click_event = event.create(callback, self)
Once an event instance is created, you can interact with it using the following methods:
event:subscribe(callback, [callback_context])
Subscribe a callback to the event. The callback will be invoked whenever the event is triggered.
-
Parameters:
callback
: The function to be executed when the event occurs.callback_context
(optional): The first parameter to be passed to the callback function.
-
Return Value:
true
if the subscription was successful,false
otherwise. -
Usage Example:
on_click_event:subscribe(callback, self)
event:unsubscribe(callback, [callback_context])
Remove a previously subscribed callback from the event.
-
Parameters:
callback
: The callback function to unsubscribe.callback_context
(optional): The first parameter to be passed to the callback function.
-
Return Value:
true
if the unsubscription was successful,false
otherwise. -
Usage Example:
on_click_event:unsubscribe(callback, self)
event:is_subscribed(callback, [callback_context])
Determine if a specific callback is currently subscribed to the event.
-
Parameters:
callback
: The callback function in question.callback_context
(optional): The first parameter to be passed to the callback function.
-
Return Value:
true
if the callback is subscribed to the event,false
otherwise. -
Usage Example:
local is_subscribed = on_click_event:is_subscribed(callback, self)
event:trigger(...)
Trigger the event, causing all subscribed callbacks to be executed.
-
Parameters: Any number of parameters to be passed to the subscribed callbacks.
-
Usage Example:
on_click_event:trigger("arg1", "arg2")
event:is_empty()
Check if the event has no subscribed callbacks.
-
Return Value:
true
if the event has no subscribed callbacks,false
otherwise. -
Usage Example:
local is_empty = on_click_event:is_empty()
event:clear()
Remove all callbacks subscribed to the event, effectively resetting it.
- Usage Example:
on_click_event:clear()
This comprehensive API facilitates the creation and management of events within your projects, enhancing modularity and interaction between different components. Enjoy the power and flexibility of the Event library in your Lua projects!
The Event library comes with a global events module that allows you to create and manage global events that can be triggered from anywhere in your game. This is particularly useful for events that need to be handled by multiple scripts or systems.
To start using the Events module in your project, you first need to import it. This can be done with the following line of code:
Global events module requires careful management of subscriptions and unsubscriptions to prevent errors.
local events = require("event.events")
events.subscribe(name, callback, [callback_context])
Subscribe a callback to the specified global event.
-
Parameters:
name
: The name of the global event to subscribe to.callback
: The function to be executed when the global event occurs.callback_context
(optional): The first parameter to be passed to the callback function.
-
Usage Example:
events.subscribe("on_game_over", callback, self)
events.unsubscribe(name, callback, [callback_context])
Remove a previously subscribed callback from the specified global event.
-
Parameters:
name
: The name of the global event to unsubscribe from.callback
: The callback function to unsubscribe.callback_context
(optional): The first parameter to be passed to the callback function.
-
Usage Example:
events.unsubscribe("on_game_over", callback, self)
events.is_subscribed(name, callback, [callback_context])
Determine if a specific callback is currently subscribed to the specified global event.
-
Parameters:
name
: The name of the global event in question.callback
: The callback function in question.callback_context
(optional): The first parameter to be passed to the callback function.
-
Return Value:
true
if the callback is subscribed to the global event,false
otherwise. -
Usage Example:
local is_subscribed = events.is_subscribed("on_game_over", callback, self)
events.trigger(name, ...)
Throw a global event with the specified name. All subscribed callbacks will be executed.
-
Parameters:
name
: The name of the global event to trigger....
: Any number of parameters to be passed to the subscribed callbacks.
-
Usage Example:
events.trigger("on_game_over", "arg1", "arg2")
events.clear(name)
Remove all callbacks subscribed to the specified global event.
-
Parameters:
name
: The name of the global event to clear.
-
Usage Example:
events.clear("on_game_over")
events.clear_all()
Remove all callbacks subscribed to all global events.
- Usage Example:
events.clear_all()
The Events module provides a powerful and flexible way to manage global events in your Defold projects. Use it to create modular and extensible systems that can respond to events from anywhere in your game.
Read the Use Cases file to see several examples of how to use the Event module in your Defold game development projects.
This project is licensed under the MIT License - see the LICENSE file for details.
Used libraries:
If you have any issues, questions or suggestions please create an issue.
Changelog
- Initial release
Changelog
- Add global events module
- The `event:subscribe` and `event:unsubscribe` now return boolean value of success
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