WoW:API select

Used to traverse a list. This function is usually used to capture the arguments passed to an ellipsis (...). The official usage of this function is to return a list (retN) starting from index to the end of the list (list).

local ret1, ret2, retN = select(index, list)

Arguments

Parameters

index

Any non-zero number or the string "#".

list

Usually an ellipsis (...).

Returns

retN

The number of items in the list or every value starting from index to the end of the list.

Examples

-- Common usage.
local num = select('#', ...) -- Returns the number of arguments in the ellipsis.
local arg = select(i, ...) -- Returns the value at index i.

-- Print all of the function's arguments (those passed to the ellipsis (...) only) to the default chat frame.
local msg
for i = 1, select('#', ...) do
    msg = select(i, ...)
    DEFAULT_CHAT_FRAME:AddMessage(msg)
end

local a, b, c = select(2, 'a', 'b', 'c')
-- a = 'b'
-- b = 'c'
-- c = nil

Catenation

select can be used to catenate a vararg list into an array. This is useful for returning info from GetBinding, which returns a vararg list of unknown size.

function MyAddon_Catenate(...)
    local t,v
    t = {}
    for i = 1, select("#", ...) do
        v = select(i, ...)
        tinsert(t, v)
    end
    return t
end

Notes

• list can be value1, value2, value3, ... valueN; although, you will never see it used in that manner since you can just access value1 through valueN directly.
• It is not recommended that you use this method on a table as you would have to pass the table to unpack() for every call to select (once plus the number of consecutive numeric indexes). For tables, use pairs() or ipairs().
• Indexes beyond the number of list items will return nil.

select(6, 'see', 'dog', 'run') -- returns nil

• An index of 0 will produce an "index out or range" error.
• Negative values wrap to the end of the list.

select(-1, 1, 2, 3, 4, 5) -- returns 5

• A decimal index will be rounded to the nearest integer (1.1 rounds to 1, 1.9 rounds to 2).
• Passing a function that returns a list as a parameter to another function will pass each return as a parameter to the function as if you were manually passing each variable to that function, so tinsert(tab, select(1, ...)), will have unpredictable results.

-- these are identical
-- number 1
local msg, r, g, b, a, id = select(1, ...)
DEFAULT_CHAT_FRAME:AddMessage(msg, r, g, b, a, id)

-- number 2
DEFAULT_CHAT_FRAME:AddMessage(select(1, ...))