Access one variable directly when more than one are returned

totebo · April 2015

When a function returns more than one variable:

function getVars()
   return var_a, var_b
end

Is it possible to get only var_b directly when calling the function? Something like:

print( getVars()[2] )

To avoid:

local var_1, var_2 = getVars()
print( var_2 )

Nic

totebo · May 2015

Rewrote this question since it's more of a straight-up Lua question rather than Box2D specifically.

keszegh · May 2015

local _, var_2 = getVars()

should work, see here:
http://stackoverflow.com/questions/3165845/how-can-i-ignore-first-results-from-a-function-in-lua

totebo · May 2015

Thanks @keszegh.

To me it seems like the cleanest solution is to add a method that returns just one specific value;

function getVarB()
   return var_b
end

My use case is getting the Y position of a Body in Box2D directly. I'm now extending the Body class with Body:getY().

Happy days.

tkhnoman · May 2015

function getVars()
   return {var_a, var_b}
end
 
print( getVars()[2] )
 
local var_1, var_2 = unpack( getVars() )

hgy29 · May 2015

What about something like that:

print(table.pack(getVars())[2])

Not that this is probably not efficient at all, but seems pretty much what you were looking for...

totebo · May 2015

Hey @hgy29, that would do it! You're right, doesn't feel like the "right" way of doing it.

@tkhnoman, that also works, but not without changing the Box2D interface unfortunately.

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