Class Template Example – Arma Reforger

A Class Template is a class definition that allows managing various types (separately) with only one declaration.

A good example that may not appear as obvious is the array class; as you may now realise, an array is simply a generic list of items where we declare the managed type on instanciation (like a set or a map), e.g:

array<string> arrayOfStrings = {}; array<bool> arrayOfBools = {}; set<int> setOfInts = new set<int>(); map<string, vector> mapOfStringsAndVectors = new map<string, vector>();

Pros	Cons
Not repeating generic code Not repeating generic code Not repeating generic code	Script Editor cannot detect an error in code unless the template is used somewhere Some silent errors can occur (e.g if (!value) check on a class instance is different from an int, etc) Too generic code may not always fit the encountered scenarios - its usage is up to the user

Examples

Below is a raw example of how to use a template, here used for casting:

class TAG_EntityCastHelper<Class T> { static T Get(Managed something) { return T.Cast(something); } static bool IsValid(Managed something) { return Get(something) != null; } static void Output(T anInstance) { if (anInstance) Print(anInstance.ToString()); } }

array<bool> anArray = {}; IEntity anEntity = EntityUtils.GetPlayer(); // provided anEntity is not null like in e.g Script Editor TAG_EntityCastHelper<IEntity> entityCastHelper = new TAG_EntityCastHelper<IEntity>(); Print("IEntity = " + entityCastHelper.IsValid(anEntity)); // IEntity = true Print("Managed = " + entityCastHelper.IsValid(anArray)); // Managed = false TAG_EntityCastHelper<Managed> managedCastHelper = new TAG_EntityCastHelper<Managed>(); Print("IEntity = " + managedCastHelper.IsValid(anEntity)); // IEntity = true Print("Managed = " + managedCastHelper.IsValid(anArray)); // Managed = true TAG_EntityCastHelper<array<bool>> boolArrayCastHelper = new TAG_EntityCastHelper<array<bool>>(); Print("IEntity = " + boolArrayCastHelper.IsValid(anEntity)); // IEntity = false Print("Managed = " + boolArrayCastHelper.IsValid(anArray)); // Managed = true TAG_EntityCastHelper<array<string>> stringArrayCastHelper = new TAG_EntityCastHelper<array<string>>(); Print("IEntity = " + stringArrayCastHelper.IsValid(anEntity)); // IEntity = false Print("Managed = " + stringArrayCastHelper.IsValid(anArray)); // Managed = false - not a string array

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Methods used on T must be generic enough; for example, T.Cast() is possible on many classes/types but e.g not on an int type - trying to use this type here raises an error.

It is also possible to use multiple types at once:

class TAG_EntityCastHelper<Class T, Class U, Class V> { protected ref array<T> m_aT = {}; protected ref array<U> m_aU = {}; protected ref array<V> m_aV = {}; static void Insert(T item1, U item2, V item3) { m_aT.Insert(item1); m_aU.Insert(item2); m_aV.Insert(item3); } static bool GetByItem1(T item1, out U item2, out V item3) { int index = m_aT.Find(item1); if (index < 0) return false; item2 = m_aU[index]; item3 = m_aV[index]; return true; } }