What am I doing wrong with pcall?

[EuroChump]

Hi,

Can anyone suggest what is wrong with the following code fragment?

The pcall if statement always returns false giving the "not possible" output.

If I remove the pcall then it works fine until I target something without morale such as a crafting node and then I get:
...\Main.lua:120: attempt to call method 'GetMorale' (a nil value)

refPlayer = Turbine.Gameplay.LocalPlayer.GetInstance();

playerTarget = Turbine.UI.Label();
playerTarget .MaxMorale = 1;
playerTarget .CurMorale = 1;


if ( refPlayer:GetTarget() ~= nil ) then
	if pcall( refPlayer:GetTarget():GetMorale() ) then 
		playerTarget.CurMorale = refPlayer:GetTarget():GetMorale();
		playerTarget.MaxMorale = refPlayer:GetTarget():GetMaxMorale();
		Turbine.Shell.WriteLine(" Updated target morale");
	else
		Turbine.Shell.WriteLine(" Not possible to get target morale");
	end
else
	Turbine.Shell.WriteLine(" No target selected");
end

What I am trying to achieve is :

if PLAYER_TARGET_NOT NULL
	if TARGET HAS MORALE
		GET_MORALE_AND_STORE_LOCALLY
	else
		DO_NOTHING
	end if
end if

and it should do this without generating errors that crash the plugin

[Garan]

First, you are not correctly calling pcall.
local success,result=pcall(function, parameters);
so your call would be something like
local success,result=pcall(Turbine.G ameplay.Actor.GetMaxMorale,ref Player);


Second, in this instance, you can't really use pcall since the GetMorale function doesn't exist for targets that have no morale. So you are passing nil to pcall instead of a function. Instead, just test whether GetMorale==nil. Note, you should also use a local to store refPlayer:GetTarget() instead of calling it so many times.

refPlayer = Turbine.Gameplay.LocalPlayer.GetInstance();

playerTarget = Turbine.UI.Label();
playerTarget.MaxMorale = 1;
playerTarget.CurMorale = 1;

local tmpTarget=refPlayer:GetTarget();

if ( tmpTarget ~= nil ) then
	if tmpTarget.GetMorale~=nil then 
		playerTarget.CurMorale = tmpTarget:GetMorale();
		if tmpTarget.GetMaxMorale~=nil then
			playerTarget.MaxMorale = tmpTarget:GetMaxMorale();
		else
			-- should really set a default when the target has no max morale, perhaps just Morale
			playerTarget.MaxMorale=playerTarget.CurMorale
		end
		Turbine.Shell.WriteLine(" Updated target morale");
	else
		Turbine.Shell.WriteLine(" Not possible to get target morale");
		-- should set morale and max morale to some default
	end
else
	Turbine.Shell.WriteLine(" No target selected");
end

Note, when comparing the function to nil, you have to use the "." syntax and no parentheses to test the function rather than the function result
The additional test for the existence of GetMaxMorale that I added is probably overkill since any target with a GetMorale function SHOULD have a GetMaxMorale, but it doesn't hurt to be safe

Alternately, you could use the IsA function to test whether refPlayer is an Actor or a Mount instead of an Item, but then if Turbine ever adds any classes of Entities, you would have to account for them so testing the existence of the GetMorale function is probably preferable.

[moebius92]

Actually, if the pcall call was correct, it should work. The problem is, the correct call is "pcall(refPlayer:GetTarget().G etMorale)".

What's happening is, the arguments of the pcall() are evaluated first. So, refPlayer:GetTarget():GetMoral e() is evaluated, and one of two things happens:

1) There is a GetMorale function, so it returns the target's morale (which is a number), and then pcall tries to perform a function call on the number (which fails, causing pcall to return false).

2) There is no GetMorale function, so the call fails, and the arguments to pcall can not be evaluated. However, since this was done in protected mode, pcall simply returns false.

On the other hand, doing the pcall correctly is roughly the equivalent of checking whether GetMorale exists in refPlayer:GetTarget().

[EuroChump]

Moebius92 - your explanation was spot on and i now appreciate why it is that pcall consistently returned false.

Garan - testing "getMorale" as you suggested is exactly what I needed and now the code is happily working as intended.

Thank you both!