WoW:API select: Difference between revisions

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


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  -- b = 'c'
  -- b = 'c'
  -- c = nil
  -- c = nil
=== Catenation ===
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(...)
    local t,v
    t = {}
    for i = 1, select("#", ...) do
        v = select(i, ...)
        tinsert(t, v)
    end
    return t
end


== Notes ==
== Notes ==
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: <pre>select(-1, 1, 2, 3, 4, 5) -- returns 5</pre>
: <pre>select(-1, 1, 2, 3, 4, 5) -- returns 5</pre>
* A decimal index will be rounded to the nearest integer (1.1 rounds to 1, 1.9 rounds to 2).
* 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.
<pre>-- these are identical
-- number 1
local msg, r, g, b, a, id = select(1, ...)
DEFAULT_CHAT_FRAME:AddMessage(msg, r, g, b, a, id)


== Disclaimer ==
-- number 2
* Tested using the command line. Lua v5.1.2. Not tested in the WoW environment.
DEFAULT_CHAT_FRAME:AddMessage(select(1, ...))</pre>
 
{{LUA}}

Latest revision as of 04:47, 15 August 2023

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[edit]

Parameters[edit]

index
Any non-zero number or the string "#".
list
Usually an ellipsis (...).

Returns[edit]

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

Examples[edit]

-- 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[edit]

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[edit]

  • 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, ...))