WoW:API select: Difference between revisions
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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). | 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) | local ret1, ret2, retN = select(index, list) | ||
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== Arguments == | == Arguments == | ||
=== Parameters === | === Parameters === | ||
:;index : Any non-zero number or the string "#". | :;index | ||
:;list : Usually an ellipsis (...). | :: Any non-zero number or the string "#". | ||
:;list | |||
:: Usually an ellipsis (...). | |||
=== Returns === | === Returns === | ||
:;retN : The number of items in the list or every value starting from index to the end of the list. | :;retN | ||
:: The number of items in the list or every value starting from index to the end of the list. | |||
== Examples == | == Examples == | ||
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=== Catenation === | === Catenation === | ||
select can be used to catenate a vararg list into an array. | select can be used to catenate a vararg list into an array. This is useful for returning info from [[API_GetBinding | GetBinding]], which returns a vararg list of unknown size. | ||
function MyAddon_Catenate(...) | function MyAddon_Catenate(...) |
Revision as of 07:32, 19 September 2013
← WoW Lua
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, ...))