jonadrian619's step by step Tutorial about Local Variables.
This is my second tutorial about JASS. This tutorial is for newbies who want to learn about local variables and even some topics about JASS..
Table of Contents:
1) Introduction
2) Creating Local Variables
3) Storing data in a Local Variable
4) Using stored data
5) Removing Memory Leaks
6) Conclusion
To know more about JASS click
here.
1) Introduction
Local variables are variables that are declared in functions. Functions are parts of the script which execute a number of actions... (click 'here' above for more details) Local variables, unlike globals, allow several copies of the trigger to fire correctly.
The only bad thing about them is that they can ONLY be used inside the function they were declared in.. The example below is wrong:
function CreateEffect
takes nothing returns nothing local unit u
set u = GetTriggerUnit
()endfunctionfunction RemoveUnit
takes nothing returns nothing call RemoveUnit
(u,
true)endfunction
Local variables also play an important role for triggered spells, most especially the spells that need dummy units to take effect.
This paragraph tells you about syntax errors. Syntax Errors are lines of script code or custom scripts that contain variables, functions or any word in the script that is incorrect, invalid or don't exist at all. You should be more careful when using WE- No Limits tool in TFT versions 1.07 or any version below 1.18, as the new GUI actions in WE no-limits will cause script errors. In this case, creating a 'Lightning Effect' action in WE no limits and you have TFT v1.07 will cause a syntax error telling that 'Lightning Effects' does not exist. To solve this problem install the latest patch.
2) Creating Local Variables
You need knowledge about JASS triggering before doing this stuff. Local variables can only be declared by using the Custom Script action.
To start, go to the Trigger Editor, then Create a new trigger or use an existing trigger. Create all the necessary events and conditions. Once finished, create a Custom Script action.
Global variables can be created in the Variable Editor, setting it's types and initial value and it's name. Local variables are declared in this manner:
local variable_type = variable_name
All variable types:
type event extends handle // a reference to an event registration
type player extends handle // a single player reference
type widget extends handle // an interactive game object with life
type unit extends widget // a single unit reference
type destructable extends widget
type item extends widget
type ability extends handle
type buff extends ability
type force extends handle
type group extends handle
type trigger extends handle
type triggercondition extends handle
type triggeraction extends handle
type timer extends handle
type location extends handle
type region extends handle
type rect extends handle
type boolexpr extends handle
type sound extends handle
type conditionfunc extends boolexpr
type filterfunc extends boolexpr
type unitpool extends handle
type itempool extends handle
type race extends handle
type alliancetype extends handle
type racepreference extends handle
type gamestate extends handle
type igamestate extends gamestate
type fgamestate extends gamestate
type playerstate extends handle
type playerscore extends handle
type playergameresult extends handle
type unitstate extends handle
type aidifficulty extends handle
type eventid extends handle
type gameevent extends eventid
type playerevent extends eventid
type playerunitevent extends eventid
type unitevent extends eventid
type limitop extends eventid
type widgetevent extends eventid
type dialogevent extends eventid
type unittype extends handle
type gamespeed extends handle
type gamedifficulty extends handle
type gametype extends handle
type mapflag extends handle
type mapvisibility extends handle
type mapsetting extends handle
type mapdensity extends handle
type mapcontrol extends handle
type playerslotstate extends handle
type volumegroup extends handle
type camerafield extends handle
type camerasetup extends handle
type playercolor extends handle
type placement extends handle
type startlocprio extends handle
type raritycontrol extends handle
type blendmode extends handle
type texmapflags extends handle
type effect extends handle
type effecttype extends handle
type weathereffect extends handle
type terraindeformation extends handle
type fogstate extends handle
type fogmodifier extends handle
type dialog extends handle
type button extends handle
type quest extends handle
type questitem extends handle
type defeatcondition extends handle
type timerdialog extends handle
type leaderboard extends handle
type multiboard extends handle
type multiboarditem extends handle
type trackable extends handle
type gamecache extends handle
type version extends handle
type itemtype extends handle
type texttag extends handle
type attacktype extends handle
type damagetype extends handle
type weapontype extends handle
type soundtype extends handle
type lightning extends handle
type pathingtype extends handle
type image extends handle
type ubersplat extends handle
Here are hard to understand types and their GUI versions
group is Unit Group in GUI
force is Player Group in GUI
destructable is Destructible in GUI
effect is Special Effect in GUI
location is Point in GUI
rect is Region in GUI
Local variables must be declared at the beginning of the function before any actions are executed, as it could cause sytnax errors.
3) Storing Data inside a Local Variable
Storing data in a local variable is similar to storing data in a global variable. The 'Set Variable' action stores data in a global variable. However, storing data in a local variable should be done in custom script:
set local variable name = value
Examples: set Nova_Caster = GetTriggerUnit() - [In GUI: Set Nova_Caster = (Triggering Unit)]
You must store data only to previously declared local variables. Also, store only data that the local variable can store. For example, you cannot store a unit into an integer local variable.
4) Using Stored Data
Once you've stored data inside a local variable, you can create any action to use the stored data. The trigger below will give an example.
local var test
When using a local variable's data make sure you use JASS or Custom Script to create the actions. GUI actions only use the data stored in a global variable. Take note that you'll create only actions that use the type of data stored in a local variable. Creating a unit using the data stored in an integer variable will cause syntax errors.
5) Removing Memory Leaks
Take note that variables leak. They will not be removed from the memory and it'll remain there. That's the main cause of in-game lag. If you've got a bunch of triggers, triggers that leak, it could cause lag and even game freezing (worst lag) when not removed for a long time. Below are ways of nullifying local variables and removing leaks.
a) Nullifying Local Variables after use
Nullifying local variables gets them out of the memory by emptying it. By setting a 'null' value to a local variable it means that it's empty. Below is an example of nullifying 2 local variables. Take note, that handles leak and must be nulled.
Nullify Test
The unit variable was declared, then when the 'GetTriggerUnit' was stored, it received a null value through the 'set' action. To nullify the string variable, let the string show off a bit, maybe 5 seconds, then add a 6 second wait action after that. Then nullify the variable.
The trigger above showed an example that the contents of the local variables must be destroyed first then nullified.
You must never nullify local variables BEFORE you destroyed what they contained, or else you'll never be able to remove that. An example of that error is like this:
Custom script: set Exploding_Unit = null
Custom script: call RemoveUnit( Exploding_Unit )
NOTE: You must pause timers and destroy their windows before you nullify them.
b) Destroying objects that cause memory leaks
This part is not related to this tutorial. However it gives newbies some tips to destroy leaks.
Points, Unit Groups, Player Groups, Special Effects, Lightning Effects, Floating Text, and Countdown Timers also leak.
Here are the actions needed to remove each of them. In order: Timer, Special Effect, Lightning Effect, Trigger, Point, Unit Group, Floating Text
Custom script: call DestroyTimer (name)
Custom script: call DestroyEffect (name)
Custom script: call DestroyLightning (name)
Custom script: call DestroyTrigger (name)
Custom script: call RemoveLocation (name)
Custom script: call DestroyGroup (name)
Custom script: call DestroyTextTag (name)
Here are additional lines to destroy handles. (Thanks to Diablo-DK)
call DestroyBoolExpr()
call DestroyCondition()
call DestroyDefeatCondition()
call DestroyFilter()
call DestroyFogModifier()
call DestroyForce()
call DestroyImage()
call DestroyItemPool()
call DestroyLeaderboard()
call DestroyMultiboard()
call DestroyQuest()
call DestroyTimerDialog()
call DestroyTrigger()
call DestroyUbersplat()
call DestroyUnitPool()
call RemoveDestructable()
call RemoveItem()
call RemoveLocation()
call RemoveRect()
call RemoveRegion()
call RemoveUnit()
call RemoveWeatherEffect()
call TriggerRemoveAction()
call TriggerRemoveCondition()
To remove a specific leaking object, an example is shown below (Point leak):
Set Temp_Point = (Center of (Playable map area))
That's all I can show you because I'm only good at GUI triggering and know few things about JASS like local variables, native functions and leaks. This is a newbie's tutorial to understanding local variables and the ways of destroying memory leaks. Learn the contents of this tutorial. There are a group of JASS tutorials in this site. Pick one of them to learn more about JASS.
Please make comments if it's enough for you or you need something more advanced.
Events
Player - Player 1 (Red) types a chat message containing - test as An Exact Match
Conditions
Actions
Custom script: local player Player_ONE
Unit - A unit Dies
Tutorial Approved
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