@soin08, thank you for these insights. Very helpful!
@Raye welcome! 
Nice to know you’re using CBEffects. Fortunately, you won’t have to worry about this, because it’s built-in in the CBEffects ‘vent.clean()’ function.
[lua]
vent:stop()
vent:clean()
[/lua]
To completely destroy the vent, you’ll need the destroy command. You’ll run into problems if you only nil out the vent, because each vent has a display group attached to it:
[lua]
vent:destroy() – Calls stop(), clean(), and removes all required objects
[/lua]
Sorry about the docs not being clearer
- C
Thank you for your response, Caleb. vent:destroy() throws me an error in the latest version of CBEffects. Please try this example:
local CBE = require("CBEffects.Library") local vent = CBE.newVent { preset = "burn" } vent:start() local function onScreenTap() vent:destroy(); end Runtime:addEventListener("tap", onScreenTap)Whoops! Should be fixed now.
- C
Awesome Thanks, Caleb!
HOLD ON. Just tried it in my app - still gives me the same error… :unsure:
Are you sure you’re not tapping more than once?
- C
Never mind, it works great. Back then I tried it in my app and it would crash, must’ve been because _destroy _was called more than once somewhere else in the code. Sorry for misleading, Caleb.
- Ilya
No problem
- C
I downloaded CBEffects today (5 Jul 2014). Since I had some problems with destroying vents so I searched the forum for this problem and found this thread. When tried soin08’s small example above it throws the following error:
File: CBEffects/cbe\_core/vent\_core/core.lua Line: 147 Attempt to index upvalue 'p' (a nil value)
When I immediately touch the screen, everything is fine. But when I wait a little longer (maybe when the first particle has died?) I get the error.
@Raye, I had the same problem in the latest version and thought the bug had not been fixed but than I tried to use a flag to make sure that the onTap event fires only once and it worked, which means there is no bug.
Ok, I added a flag. And I still got the same error (most of the time, not always). So I added some print statements, to see whats going on.
-------------------------------------------------------------------------------- -- main.lua -------------------------------------------------------------------------------- display.setStatusBar(display.HiddenStatusBar) -------------------------------------------------------------------------------- -- Create Sample Effect -------------------------------------------------------------------------------- local CBE = require("CBEffects.Library") local isDestroyed = false local vent = CBE.newVent { preset = "burn" } vent:start() local function onScreenTap() print("onScreenTap() - isDestroyed -\> " .. tostring(isDestroyed)) if isDestroyed == false then print("vent = " .. tostring(vent) ) vent:destroy() isDestroyed = true print("vent destroyed - isDestroyed -\> " .. tostring(isDestroyed)) print("vent = " .. tostring(vent) ) end end Runtime:addEventListener("tap", onScreenTap)
Sometimes it works, but sometimes I get the error as mentioned above. As far as I can tell from the console output the vent:destroy() is called only once. Or am I wrong?
@Raye, you’re right… I too get that error sometimes. You can use my solution until this gets fixed. Or could it be a Corona bug? Let’s see what Caleb (the creator of the amazing CBEffects) thinks about it.
For me it works fine like 9 times out of 10 on avarage.
@sonoi08 Phew, I’m glad you get the error, too. :lol:
As far as have looked at the code the p._kill() function tries to kill a p that has a nil value. I put a
if p == nil then return end
at the beginning of p._kill() but I don’t know if this good programming practice in Corona/Lua.
I’m relative new to Corona and Lua. In the Examples/Tuts/Docs I have never seen practices that an object is checked if it is nil before deleting/working on it. But I know this practice from other programming languages.
Ok, let’s see if Caleb can help.
@Raye, such practicies do exist in Lua. For example in this topic @Roaminggamer talks about how you can determine wheter a displayObject has been removed to safely use the _onComplete _function passed to the transition. I use a different method btw.
@soin08 Ah thank you. Your technique with storing the transitions in a table and cancel is even more elegant.
Right now the hardest part for me in Corona developing is to really clean up a complex scene with (OOP objects and inheritance objects) when it comes to transition to a different scene. It is rather frustrating: the ingame works really nice, but such a thing like simple transition to the menu (or an pause overlay) really bothers me.
Thanks for alerting me of this, it should be fixed now.
Explanation? CBEffects uses internally a structure called a VS-T (I can’t remember what it stands for; it had a meaning months ago when I created it ), which allows you to mark objects for removal from it. Then, whenever you want, you can clear those objects. Kind of like a delayed table.remove.
Anyhow and anyhoo, when a particle is ._kill()-ed, it’s marked for removal in the VS-T particle container. CBEffects clears the particle container every few frames, so there are “dead” particle references in there most of the time. When you call vent:destroy(), CBEffects iterates through all particles in that container and calls ._kill() on them - including the ones that have been marked for removal already. Obviously, if the container hasn’t been cleared at that instant, it tries to ._kill() particles that are already “dead”, which creates that error. I just uploaded a fix that clears the particle container right before iterating through them, so it’s fixed.
- C
@Caleb Tested and working! Cool! Thank you for this fast fix and explanation and this great module at all.
No problem
- C