To solve how to reset boolean in defold, assign self.my_flag = false inside any script lifecycle function like on_message or update. Defold uses standard Lua state tables, so writing the variable name on self immediately replaces its current truthy value with false or nil in memory.
Variables attached to self belong only to that specific script instance. If you create a plain variable without writing self. before it, you accidentally make it global, which breaks other game objects.
This guide isn’t for people using Defold’s visual tilemap layers or raw gui text properties without a script component.
Steps to Reset a Boolean in Defold
- Open your game object’s
.scriptfile in the Defold editor by double-clicking it in the Assets panel. - Locate your
init(self)function and typeself.is_active = trueto establish the initial boolean state. - Scroll to the function where the reset event occurs, such as
on_message(self, message_id, message, sender). - Add an
ifstatement matching your trigger, likeif message_id == hash("reset") then. Tip: If X is an external message, use hashes; if Y is an internal timer, usetimer.delay(). - Write
self.is_active = falseinside the block to flip the value back. - Check the official Defold Lua script documentation if you need to pass this state across different collections.
- Save the script file using Ctrl+S (or Cmd+S on Mac) so the engine bundles the updated code.
How Long It Takes
Updating and testing a boolean reset takes only seconds in the editor.
| Situation | How long | What changes it | What to watch for |
|---|---|---|---|
| Single script flag | 10 to 30 seconds | Typing speed | Missing the self. prefix |
| Delayed reset timer | 1 to 2 minutes | Callback setup | Passing the wrong context to callback |
| Inter-script reset | 2 to 5 minutes | Message bus routing | Typos in the string inside hash() |
If testing takes longer than five minutes, your script probably has an execution error that halts processing before reaching your reset line.
How to Tell When It’s Done
Add print("Flag state:", self.is_active) directly below your assignment line and press Ctrl+B to run the project. Open the engine console output panel at the bottom of the editor. If the boolean reset correctly, the console prints Flag state: false the exact moment your trigger fires. The definitive test is wrapping your logic in if not self.is_active then: if the gated action stops running, the flag cleared properly. Remember, Lua treats only false and nil as falsy values; the number 0 evaluates to true.
Mistakes That Ruin It
- Omitting the self prefix: Writing
is_active = falsecreates a global variable across the entire Lua runtime. That shared flag unintentionally overwrites states across every spawned enemy or item instance, so always writeself.is_active. - Setting the flag to zero: Putting
self.is_active = 0leaves the condition truthy because Defold’s Lua engine only treatsfalseandnilas false. Always use the literal keywordfalsewhen clearing flags. - Typing errors inside hash functions: Using
hash("Reset")with a capital letter fails to match a message sent as"reset". Match your casing letter-for-letter to ensure message triggers execute.
Frequently Asked Questions
Can You Reset a Boolean Using a Timer?
Yes. Use timer.delay(2, false, function() self.my_flag = false end) to reset it after two seconds. This timer assumes your script component remains alive; destroying the game object before the timer finishes cancels the pending callback automatically.
What Happens If You Set a Boolean to Nil?
Setting it to nil removes the variable key from the self table completely. Lua treats nil as false in conditional checks, so if not self.my_flag then still works, but reading the key yields no stored value.
Why Does My Boolean Stay True After Changing It?
Another function is likely setting it back to true on every frame. Check your update(self, dt) function to confirm you don’t have code continuously overwriting your reset logic.
Is It Safe to Reset Flags Across Different Game Objects?
Yes, but you must send a message using msg.post("url", "reset_flag") instead of altering external variables directly. Defold isolates script environments, so game objects can’t directly access each other’s private self tables.
How Do You Toggle a Boolean Instead of Resetting It?
Write self.my_flag = not self.my_flag on the trigger line. That line reverses the current value, turning true into false and false into true in a single operation.
