I have a need to write some Lua code but having come from a C background some of the common practices and programming strategies seem unusual to me. That said I wrote some code that illustrates what I am having trouble with:
local someFunction(myName)
local fallbackTable = {name = ""}
local myTable = getTableOrReturnNil(someArgument) or fallbackTable
local otherName = myTable["name"]
--other code that is irrelevant
end
My question is specifically regarding the line local myTable = getTableOrReturnNil(someArgument) or fallbackTable. From what I understand this expression will evaluate to fallbackTable if the return value from getTableOrReturnNil() return nil. It may be worth mentioning that I do not have control over the function getTableOrReturnNil(). Is this a common practice or is there a more standard way to do local otherName = myTable["name"] safely without having to worry about if myTable is nil. I can resort to using a chain of if's but I would rather avoid this if possible.
Fallback values in functions are, especially for optional parameters. Maybe not entire tables as often, but it's not unheard of.
local function clamp( value, minimum, maximum )
minimum = minimum or 0
maximum = maximum or 255
return math.min( math.max( value, minimum ), maximum )
end
print( clamp( -50 ), clamp( 50 ), clamp( 500 ) )
0 50 255
With tables, you're more likely to see metatables used when a value isn't present.
mytable = { name = 'nomer' }
meta = { __index = function( tbl, key ) return 'misnomer' end }
setmetatable( mytable, meta )
print( mytable['name'], mytable['noname'] )
nomer misnomer