LUA script error : event.initiator

[d0ppler]

On some very rare occasions, I get error in my script, when trying event.initiator:getName(), though I test event.initiator for nil before I try to get its name. Does this mean that event.initiator doesn't necessary have the getName() function?

The problem is that it's hard to replicate, since it almost NEVER occurs, only occasionally. 
Is there any safer way around this, to avoid this error?

shootingHandler = {}
function shootingHandler:onEvent(event)
    if event.id == world.event.S_EVENT_HIT then
        if event.target.getCoalition and event.initiator then
            local a = event.initiator:getName() -- here is where it breaks, since getName() on rare occasions returns nil
        end
    end      
end
world.addEventHandler(shootingHandler)

 

Should I test for event.initiator:getName() rather than event.initiator ?

Edited October 22 by d0ppler

[Mistermann]

Not sure if @cfrag is back these days, but he'd likely have a pretty good response.

[d0ppler]

I've changed the script to

if event.target.getCoalition and event.initiator:getName() then

And so far it works (like it used to do). Lets hope this little tweak irons out the potential bug

[Draken35]

What error do you exactly get?
Hit event initiators should be an unit object with a getName().
It is been a while but if I recall correctly I got into a similar issue with Hit event detecting the initiator when the target was hit with the bomblets of cluster bombs.

10 minutes ago, d0ppler said:

 

if event.target.getCoalition and event.initiator:getName() then

 

That will fail if initiator is nil
you can use a pcall to test the getName() 

if event.target.getCoalition and event.initiator then
     local status, a= pcall(function(p) return p:getName() end,event.initiator)
 end

if status is true, a has whatever getName returned. If status is false, a will have the error description

Edited October 22 by Draken35

[d0ppler]

Thanks, Draken35!

I've now changed it (once more) to:

shootingHandler = {}
function shootingHandler:onEvent(event)
    if event.id == world.event.S_EVENT_HIT then
        if event.target.getCoalition and event.initiator then
            local a = ""
            pcall(function() if event.initiator and event.initiator.getName then a = event.initiator:getName() end end)
        end
    end      
end
world.addEventHandler(shootingHandler)

 

[Draken35]

10 minutes ago, d0ppler said:

Thanks, Draken35!

I've now changed it (once more) to:

shootingHandler = {}
function shootingHandler:onEvent(event)
    if event.id == world.event.S_EVENT_HIT then
        if event.target.getCoalition and event.initiator then
            local a = ""
            pcall(function() if event.initiator and event.initiator.getName then a = event.initiator:getName() end end)
        end
    end      
end
world.addEventHandler(shootingHandler)

 

 

My pleasure!
You are missing a () after the getName in the and.

Also, what was the error you were getting? That initiator did not had a getName() function?

Edited October 22 by Draken35

[Draken35]

Ohhhh! This was for Polar Shield?

Thanks for the campaign! It is my queue to fly it

[d0ppler]

The error was the standard "nil" value error

I'm using ".", not ":" to test this.

event.initiator.getName

 

I think it's correct to not use "()", or?

Yes, its for polar shield

[Draken35]

3 minutes ago, d0ppler said:

The error was the standard "nil" value error

I'm using ".", not ":" to test this.

event.initiator.getName

 

I think it's correct to not use "()", or?

Yes, its for polar shield

Ah! I see what you mean.. Never thought of testing the existence of a method that way... Gotta test that later

And that was a weird error... I can see an initiator not existing when hit event triggers (long range weapon and initiator destroyed before it reaches the target) but since the initiator should be an unit, it has to have the method... Anyway, it would be interesting to dump the whole initiator object to the log to see what it is in there.

[d0ppler]

5 minutes ago, Draken35 said:

Never thought of testing the existence of a method that way

I believe it uses a tiny bit less of cpu resources rather than check the actual value itself.

[Tobias00723]

I would recommend taking a look here -> 

This explains it very well why objects can give nil errors

[kira_mikamy]

In a S_EVENT_HIT event, the event.initiator can sometimes be the ammunition object instead of the firing unit.
Since ammunition objects don’t have a getName() method, calling it directly will return nil.

To avoid this, you need to check that the initiator is a valid unit before trying to get its name.
This can be done by verifying its object category.