Default values not working??

antix

Hey all. I am setting up an actor in my game engine with a table of options but something is not quite working when I go to set a default property if the option is missing from the table....

local function addActor1(options) local actor = {} actor.shrinks = options.shrinks or false print(actor.shrinks) end   local function addActor2(options) local actor = {} actor.shrinks = options.shrinks or true print(actor.shrinks) end

Calling either function with a blank table for options works fine. If I call addActor1({shrinks = true}), then actor.shrinks is TRUE as I would expect. If I call the addActor2({shrinks = false}) however, actor.shrinks is still TRUE! Why is it not false?

I thought if shrink has been specified then that value would be used, and if shrink was not specified then the default TRUE would be used.

Am I missing something simple here (as per usual)??

ar2rsawseen

@antix problem is that or is a boolean expression
and what you are doing is evaluating

false or true, which will always be true.

You can do such default value assignment but, not with booleans (or probably even not numbers)

you would need to explicitly check if it is nil

if options.shrink == nil then options.shrink = true end

Fyfff

Man, you set "shrinks = false" so when Lua check the condition with "or" it think that the first argument == false and then return the second argument (it's a rule of "or" expression). You've better use another flag, like "0" or string "false".

Oh, you also can use that

actor.shrinks = true and options.shrinks

mad, but valid

antix

@ar2rsawseen thanks. I am having success with numbers though

@Fyfff awesome, I'll use that since it's less code

Fyfff

@antix
Btw, this code will return "nil" if you don't set the "shrinks" field explicitly. If you want to have "true" when "shrinks" doesn't set you need smth like this:

actor.shrinks = true and (options.shrinks == nil or options.shrinks)

antix

@Fyfff ahh okay cheers. Its all working now and I can move on from particle systems to something interesting like animation systems *yawn* )