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/8.zip
Note: The library size is calculated based on the build report per platform
Platform | Library Size |
---|---|
HTML5 | 2.07 KB |
Desktop / Mobile | 3.54 KB |
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.
The event memory tracking is not 100% accurate and is used to check unexpected huge leaks in the event callbacks. The memory tracking applied additional memory allocations for tracking purposes.
Memory allocation tracking is turned off in release builds, regardless of the game.project
settings.
-- Event Module
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()
event.set_logger(logger)
event.set_memory_threshold(threshold)
-- Global Events Module
events.subscribe(name, callback, [callback_context])
events.unsubscribe(name, callback, [callback_context])
events.is_subscribed(name, callback, [callback_context])
events.trigger(name, ...)
events.is_empty(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")
event.create(callback, [callback_context])
Generate a new event instance. This instance can then be used to subscribe to and trigger events. The callback
function will be called when the event is triggered. The callback_context
parameter is optional and will be passed as the first parameter to the callback function. Usually, it is used to pass the self
instance. Allocate 64
bytes per instance.
-
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 function callback(self)
print("clicked!")
end
function init(self)
self.on_click_event = event.create(callback, self)
end
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. The callback_context
parameter is optional and will be passed as the first parameter to the callback function. If the callback with context is already subscribed, the warning will be logged. Allocate 160
bytes per first subscription and 104
bytes per next subscriptions.
-
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. The callback_context
should be the same as the one used when subscribing the callback. If there is no callback_context
provided, the warning will be logged.
-
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. The callback_context
should be the same as the one used when subscribing the callback.
-
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. Any parameters passed to trigger
will be forwarded to the callbacks. The return value of the last executed callback is returned. The event:trigger(...)
can be called as event(...)
.
-
Parameters: Any number of parameters to be passed to the subscribed callbacks.
-
Return Value: The return value of the last callback executed.
-
Usage Example:
on_click_event:trigger("arg1", "arg2")
-- The event can be triggered as a function
on_click_event("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()
Customize the logging mechanism used by Event module. You can use Defold Log library or provide a custom logger. By default, the module uses the pprint
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)
Set the threshold for logging warnings about memory allocations in event callbacks. Works only in debug builds. The threshold is in kilobytes. If the callback causes a memory allocation greater than the threshold, a warning will be logged.
event.set_memory_threshold(threshold)
-
Parameters:
threshold
: Threshold in kilobytes for logging warnings about memory allocations.0
disables tracking.
-
Usage Example:
event.set_memory_threshold(50)
event.set_memory_threshold(0) -- Disable tracking
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:
function init(self)
events.subscribe("on_game_over", callback, self)
end
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:
function final(self)
events.unsubscribe("on_game_over", callback, self)
end
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. Any parameters passed to trigger
will be forwarded to the callbacks. The return value of the last executed callback is returned.
-
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.is_empty(name)
Check if the specified global event has no subscribed callbacks.
-
Parameters:
name
: The name of the global event to check.
-
Return Value:
true
if the global event has no subscribed callbacks,false
otherwise. -
Usage Example:
local is_empty = events.is_empty("on_game_over")
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
Changelog
- Event Trigger now returns value of last executed callback
- Add `events.is_empty(name)` function
- Add tests for Event and Global Events modules
Changelog
- Rename `lua_script_instance` to `event_context_manager` to escape conflicts with `lua_script_instance` library
- Fix validate context in `event_context_manager.set`
- Better error messages in case of invalid context
- Refactor `event_context_manager`
- Add tests for event_context_manager
- Add `event.set_memory_threshold` function. Works only in debug builds.
Changelog
- The `event:trigger(...)` can be called as `event(...)` via `__call` metamethod
- Add default pprint logger. Remove or replace it with `event.set_logger()`
- Add tests for context changing
Changelog
- Optimize memory allocations per event instance
- Localize functions in the event module for better performance
Changelog
- Optimize memory allocations per event instance
- Default logger now empty except for errors
Changelog
- Optimize memory allocations per subscription (~35% less)
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