forEach: Difference between revisions

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(Rewrite confusing and errornous note)
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<dl class="command_description">
<dl class="command_description">
<dd class="notedate">Posted on June 17, 2016 - 21:51 (UTC)</dd>
<dd class="notedate">Posted on November 28, 2017 - 13:46 (UTC)</dd>
<dt class="note">[[User:Killzone Kid|Killzone Kid]]</dt>
<dt class="note">[[User:dedmen|dedmen]]</dt>
<dd class="note">
<dd class="note">
To be more precise, '''_forEachIndex''' represents NOT the index of the current array element, but the number of the loop iteration. If array is modified by reference while it is iterated through with [[forEach]] loop, '''_forEachIndex''' will NOT change to reflect that. For example:
Be careful when deleting ([[deleteAt]]) elements from an Array while you iterate over it.<br>
<code>_array = ["1","2","3","4","5","6","7","8","9"];
[[forEachIndex|_forEachIndex]] will not move to reflect your change.<br>
{
[[systemChat]] str [_x, _forEachIndex, _array];
_array [[deleteAt]] _forEachIndex;
}
[[forEach]] _array;


/*result:
The forEach code is doing the same as
[_x, _forEachIndex, _array]
<code>
["1",0,["1","2","3","4","5","6","7","8","9"]]
_forEachIndex = 0;
["3",1,["2","3","4","5","6","7","8","9"]]
while {_forEachIndex < count _array} do {
["5",2,["2","4","5","6","7","8","9"]]
    (_array select _forEachIndex) call code;
["7",3,["2","4","6","7","8","9"]]
    _forEachIndex = _forEachIndex + 1;
["9",4,["2","4","6","8","9"]]*/
}
</code>
</code>
So if you delete your current element from the array the other elements will shift forward. Meaning you skip one element.<br>
Example:
<code>_array = [1,2,3,4,5,6];
{_array deleteAt _forEachIndex} forEach _array;
</code>
After the first iteration your Array will be [2,3,4,5,6] and the _forEachIndex will be 1.<br>
So on next iteration you get the element at index 1 which will be 3. So you've just skipped the 2.<br>
So in the end you will only iterate over 1,3 and 6
</dd>
</dd>
</dl>
</dl>
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Revision as of 14:46, 28 November 2017

Hover & click on the images for description

Description

Description:
Executes the given command(s) on every item of an array.
The array items are represented by the magic variable _x. The array indices are represented by _forEachIndex.
In ArmA2 & VBS2, the variable _x is always local to the forEach block so it is safe to nest them.
Groups:
Uncategorised

Syntax

Syntax:
script forEach array
Parameters:
script: String or Code (OFP / Arma)
array: Array
Return Value:
Anything - will return the value of last executed statement

Examples

Example 1:
{ _x setDammage 1; } forEach units group player;
Example 2:
This command can also easily be used to execute a single command multiple times without respect to the array items. { player addMagazine "M16"; } forEach [1, 2, 3, 4];
Example 3:
You can also use multiple commands in the same block. { _x setCaptive true; removeAllWeapons _x; doStop _x; } forEach units group this;
Example 4:
To get the index of a forEach loop, use _forEachIndex. {systemChat format ["%1", _forEachIndex];} forEach [1,2,3]; Will return: "0", "1", "2" in systemChat messages.

Additional Information

See also:
setresizepushBackpushBackUniqueapplyreverseselectinfindtoArraytoStringcountdeleteAtdeleteRangeappendsortparamparamsarrayIntersectControl StructuressplitStringjoinString

Notes

Report bugs on the Feedback Tracker and/or discuss them on the Arma Discord or on the Forums.
Only post proven facts here! Add Note

Notes

Posted on July 20, 2010
Kronzky
If arrays are used in forEach loops, _x uses them by reference, so any changes to _x will be applied to the original: _arr1 = [1,2,3]; _arr2 = [6,7,8]; {_x set [1,"x"]} forEach [_arr1,_arr2]; will change _arr1 to [1,"x",3], and _arr2 to [6,"x",8].

Bottom Section

Posted on August 29, 2014 - 22:23 (UTC)
Fett Li
forEach returns any (the last passed value will be the return value or just Nothing, depends on the function called). _var = {_x} forEach [ nil,"s",objNull,configFile ]; // return bin\config.bin _var = {_x setCaptive true} forEach allUnits; // return nothing
Posted on September 20, 2014
Mossarelli
Using the foreach loop, since there are no variable for the index like say the for-do loop, there is a variable that you can use to check the index of the foreach loop. { if (_forEachIndex == 1) then { // Copilot _x addUniform "U_B_Soldier_VR"; } else { // Adams [_x, "B_Soldier_TL_F"] call BIS_fnc_loadInventory; _x addUniform "U_B_Soldier_VR"; _x setIdentity "Bootcamp_B_Adams"; }; } forEach _crew; So when the array is past from _crew to the loop, index 1 (which is the second element) is the copilot of the "B_Heli_Light_01_F" and he will get "U_B_Soldier_VR" as a uniform. While the pilot which is index 0 (first element), will get the same uniform but will get the loadout of "B_Soldier_TL_F" and the identity of "Bootcamp_B_Adams".
Posted on January 2, 2015 - 22:35 (UTC)
Heeeere's Johnny!
Using exitWith inside a forEach loop will make forEach actually return something, namely whatever the exitWith returns: _result = { if(_x isEqualTo 3) exitWith {"Hello"} } forEach [1,2,3,4,5]; //_result = "Hello"
Posted on November 28, 2017 - 13:46 (UTC)
dedmen
Be careful when deleting (deleteAt) elements from an Array while you iterate over it.
_forEachIndex will not move to reflect your change.
The forEach code is doing the same as _forEachIndex = 0; while {_forEachIndex < count _array} do { (_array select _forEachIndex) call code; _forEachIndex = _forEachIndex + 1; } So if you delete your current element from the array the other elements will shift forward. Meaning you skip one element.
Example: _array = [1,2,3,4,5,6]; {_array deleteAt _forEachIndex} forEach _array; After the first iteration your Array will be [2,3,4,5,6] and the _forEachIndex will be 1.
So on next iteration you get the element at index 1 which will be 3. So you've just skipped the 2.
So in the end you will only iterate over 1,3 and 6