Re: Safe navigation operator

[Wesley Smith <wesley.hoke@...>]

> So the next step was "Well Lua is wonderful, it'll be easy to implement that 'specific' behavior with metamethods!". But after a little though and tries out, I realized that this use case was not coverable with __index / __newindex, because those metamethods lacks a 'context'.
>
> Does somebody already encountered/solved that use case ?

Usually the context is the table itself

function __index(t, k)
function __newindex(t, k, v)

where t is the context

Otherwise, just do

myable.optional_value = mytable.optional_value and
mytable.optional_value or "DEFAULT"

This is the typical Lua idiom for setting default values.  Be careful
if the value is a boolean though since the and/or ops will work
differently.  In that case, you actually have to check the type of the
value.

wes