Lua Functions Named Arguments


local function A(name, age, hobby)
    print(name .. "is " .. age .. " years old and likes " .. hobby)
A("john", "eating", 23) --> prints 'john is eating years old and likes 23'
-- oops, seems we got the order of the arguments wrong...
-- this happens a lot, specially with long functions that take a lot of arguments
-- and where the order doesn't follow any particular logic

local function B(tab)
    print( .. "is " .. tab.age .. " years old and likes " .. tab.hobby)
local john = {name="john", hobby="golf", age="over 9000", comment="plays too much golf"}
--> will print 'John is over 9000 years old and likes golf'
-- I also added a 'comment' argument just to show that excess arguments are ignored by the function

B({name = "tim"}) -- can also be written as
B{name = "tim"} -- to avoid cluttering the code
--> both will print 'tim is nil years old and likes nil'
-- remember to check for missing arguments and deal with them

function C(tab)
    if not tab.age then return nil, "age not defined" end
    tab.hobby = tab.hobby or "nothing"
    -- print stuff

-- note that if we later decide to do a 'person' class
-- we just need to make sure that this class has the three fields
-- age, hobby and name, and it will be compatible with these functions

-- example:
local john ="John", 20, "golf") -- some sort of constructor
john.address = "some place" -- modify the object
john:do_something("information") -- call some function of the object
C(john) -- this works because objects are *usually* implemented as tables