Using Dynamic Arrays in UnrealScript

Dynamic Array is a collection of data items that can be resized during the execution of the game.

A Dynamic Array is a variable type declared as follows:

var array < arrayType > arrayName ;

The array type can be primitives such as int and float or any class such as Actor and Pawn.

A Dynamic Array can also be defined as local variable within a function using the keyword "local".

The current size of a Dynamic Array can be found in their Length attribute. Access to the individual elements of a Dynamic Array can be done with an index in the same way as in a static array. Remember that the index of an array always starts from 0.

A simple example using Dynamic Array:

class EnemyTypes extends Actor;

var array <int> enemyTypeList;


function int getEnemyType(int index)
{
    if(index < 0 || index >= enemyTypeList.Length) 
    {
        return -1;  // Error: Invalid Index
    } 
    else 
    {
        return enemyTypeList[ index ];
    }
}

function setEnemyType(int index, int enemyType)
{
    if(index >= 0 && enemyType >= 0)
    {
        enemyTypeList[ index ] = enemyType;
    }
}

Note that in the above example, in the function setEnemyType(), there is no problem if the index is greater than the current size of the array, because a Dynamic Array will increase its size to store the required index.

There are some functions that are part of a Dynamic Array. Below are the main ones:

• AddItem( Element ): Adds an Element to the end of the Dynamic Array. The Element must be the same type of the Dynamic Array.

• RemoveItem( Element ): Removes an Element of the Dynamic Array.

• InsertItem( int Index, Element): Inserts an Element in the Dynamic Array at the specified index.

• Find( Element ): Search for the Element within the Dynamic Array and returns the index of the found element, or "-1" if not found.

I did an example that creates a random amount of Shield Belts (class UTGameContent.UTDroppedShieldBelt) in random positions. The Shield Belts instances that were created are added to a Dynamic Array. After creating all Shield Belts, the Dynamic Array is iterated using the ForEach operator to register in the Log the position of each Shield Belt created.

Code and image of this example:

class TestDynamicArrays extends UTGame;

var array <UTDroppedShieldBelt> shieldList;

function StartMatch()
{
    local UTDroppedShieldBelt shieldInstance;    
    local vector shieldLocation;
    local int totalShields;    
    
    super.StartMatch();

    totalShields = 10 + Rand(10);     
    
    do
    {
        //Choose a random position
        shieldLocation.X = -1000 + Rand(2001); //-1000 to 1000;
        shieldLocation.Y = -1000 + Rand(2001); //-1000 to 1000;
        shieldLocation.Z = 50 ;
    
        shieldInstance = spawn(class 'UTGameContent.UTDroppedShieldBelt', , ,shieldLocation);
        
        shieldList.addItem( shieldInstance );        
                
    } until ( shieldList.Length == totalShields ) ;
    
    `Log("TOTAL OF SHIELDS =" @ shieldList.Length);
    
    //write in the log the position of all shields
    foreach shieldList( shieldInstance )
    {
      `Log( "Location =" @ shieldInstance.Location );
    }
}

This log shows what was registered in one of the executions of the example.

[0294.02] ScriptLog: TOTAL OF SHIELDS = 18
[0294.02] ScriptLog: Location = -390.00,183.00,50.00
[0294.02] ScriptLog: Location = -946.00,-300.00,50.00
[0294.02] ScriptLog: Location = -101.00,133.00,50.00
[0294.02] ScriptLog: Location = 225.00,701.00,50.00
[0294.02] ScriptLog: Location = 611.00,-908.00,50.00
[0294.02] ScriptLog: Location = -650.00,-532.00,50.00
[0294.02] ScriptLog: Location = -550.00,449.00,50.00
[0294.02] ScriptLog: Location = -245.00,531.00,50.00
[0294.02] ScriptLog: Location = 307.00,-890.00,50.00
[0294.02] ScriptLog: Location = -14.00,-534.00,50.00
[0294.02] ScriptLog: Location = -191.00,101.00,50.00
[0294.02] ScriptLog: Location = -756.00,832.00,50.00
[0294.02] ScriptLog: Location = 796.00,390.00,50.00
[0294.02] ScriptLog: Location = -833.00,-915.00,50.00
[0294.02] ScriptLog: Location = 780.00,-248.00,50.00
[0294.02] ScriptLog: Location = 492.00,841.00,50.00
[0294.02] ScriptLog: Location = 461.00,-526.00,50.00
[0294.02] ScriptLog: Location = 179.00,-266.00,50.00