Scripting: Keywords – Arma Reforger

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Revision as of 21:00, 17 May 2022

Class Keywords

class

 Declares a class 
class ExampleClass
{
}

modded

 See Modded Class 
class ExampleClass
{
}
 
modded class ExampleClass // inherits and "takes the place" of the original ExampleClass
{
}

sealed

 A class marked with the sealed keyword cannot be inherited from 
sealed class Infertile
{
}
 
class Child : Infertile // compilation error - a class cannot inherit from a sealed class
{
}

extends

 states that the declared class inherits from another 
class ChildClass extends ParentClass
{
}
 
// alias
class ChildClass : ParentClass
{
}

typedef

 Declares an alias for a type 
typedef string Text;
 
class ExampleClass
{
	Text m_sMyText = "This is my text, that is a string";
}


Method Keywords

proto

 Prototyping of internal function (Engine side).

native

 Native call convention of internal function (Engine side).

volatile

 Internal function that may call back to script (hint for compiler that context need to be saved on stack).

private

 Modifier for class method. The method can be called only from inside of the same class' methods. A modded class will not be able to use it either. 
class ExampleClass
{
	private void HelloWorld()
	{
		Print("Hello there");
	}

	void PublicHelloWorld()
	{
		HelloWorld(); // works from within the object
	}
}
 
ExampleClass classInstance = new ExampleClass();
classInstance.PublicHelloWorld();	// works - calls PublicHelloWorld() that calls HelloWorld()
classInstance.HelloWorld();			// compilation error - HelloWorld() is private and cannot be accessed

protected

 Modifier for class method. The method can be called only from inside of class' methods or methods of its extended (children) classes, or a modded class. 
class ParentClass
{
	protected void HelloWorld()
	{
		Print("Hello there");
	}
}

class ChildClass : ParentClass
{
	void PublicHelloWorld()
	{
		HelloWorld(); // works from within the object
	}
}
 
ChildClass classInstance = new ChildClass();
classInstance.PublicHelloWorld();	// works - calls PublicHelloWorld() that calls HelloWorld()
classInstance.HelloWorld();			// compilation error - HelloWorld() is protected and cannot be accessed
 
ParentClass classInstance = new ParentClass();
classInstance.HelloWorld();			// compilation error - HelloWorld() is protected and cannot be accessed

static

 Modifier for class method. The method can be called without object pointer, just by ClassName.methodName(). Only static values/methods can be accessed from a static method. 
class ExampleClass
{
	static void HelloWorld()
	{
		Print("Hello there");
	}
}
 
ExampleClass.HelloWorld();	// works
 
ExampleClass classInstance = new ExampleClass();
classInstance.HelloWorld();	// works

event

 Hint for tools that the function should be exposed as Entity script event.

override

 Modifier for class method indicating overriding of base class method. Compiler checks if is method present in base class and if method signature matches. 
class ParentClass
{
	void HelloWorld()
	{
		Print("Hello world");
	}
}

class ChildClass : ParentClass
{
	override void HelloWorld()
	{
		Print("Hello there");
	}
}
 
ParentClass parentClassInstance = new ParentClass();
parentClassInstance.HelloWorld();	// prints "Hello world"
 
ChildClass childClassInstance = new ChildClass();
childClassInstance.HelloWorld();	// prints "Hello there"

sealed

 Modifier for class method. The method cannot be overridden in derived classes. 
class ParentClass
{
	sealed void HelloWorld()
	{
		Print("Hello there");
	}
}
 
class ChildClass : ParentClass
{
	override void HelloWorld() // compilation error - cannot override a sealed method
	{
		Print("Hello world");
	}
}


Value Keywords

owned

 Modifier for returning internal functions. Tells to script-VM that returning variable (string or array) must not be released.

out

 Modifier for function parameters. It tells that variable will be changed by function call. 
void Method(out array<string> parameter)
{
	parameter = new array<string>();
	parameter.Insert("Hello");
	parameter.Insert("there");
}
 
// ...
 
array<string> myArray = null;
Method(array); // myArray is now { "Hello", "there" }

inout

 Modifier for function parameters. It tells that variable will be used and then changed by function call. 
class ExampleClass
{
	private ref array<string> m_aList;

	void Method(inout array<string> parameter)
	{
		parameter = new array<string>();
		parameter.Insert("Hello");
		parameter.Insert("there");

		m_aList = parameter;
	}
}
 
ExampleClass classInstance = new ExampleClass();
 
array<string> myArray = null;
classInstance.Method(array); // myArray is now { "Hello", "there" } and classInstance.m_aList is referencing myArray

const

 Declares a constant, that is a value that cannot be modified later. 
const string MY_TEXT = "Hello there";
 
void Method()
{
	Print(MY_TEXT); // will print "Hello there"
	MY_TEXT = "General Kenobi"; // compilation error - a constant is set in stone and cannot be modified
}

reference

 Hint for tools (Material editor) that the value may be used as parameter in material.

notnull

 Modifier for function parameter of class pointer type. It tells that function expect the parameter will never be null. It shows error eventually and function won't be called. 
void Method(notnull IEntity entity) // no need to check for "if (!entity)" inside the method
{
	entity.DoSomething(); // the argument can be accessed safely
}
 
if (myEntity) // it is still needed to check for null before calling the method
{
	Method(myEntity);
}

private

 Value can only be accessed from the class/instance methods. Mutually exclusive with "protected". 
class ExampleClass
{
	private bool m_bIsActive;

	void SetActive(bool value)
	{
		m_bIsActive = value;
	}
}
 
ExampleClass classInstance = new ExampleClass();
Print(classInstance.m_bIsActive); // compilation error - m_bIsActive is private and cannot be accessed

protected

 Value can only be accessed from the class/instance methods or its children. Mutually exclusive with "private". 
class ParentClass
{
	protected bool m_bProtected;
	private bool m_bPrivate;

	void SetPrivate(bool value)
	{
		m_bPrivate = value;
	}
}
 
class ChildClass : ParentClass
{
	void SetProtected(bool value)
	{
		m_bProtected = value; // works - m_bProtected declaration reaches ChildClass
	}
}
 
ChildClass childClassInstance = new ChildClass();
Print(childClassInstance.m_bProtected); // compilation error - m_bProtected is protected and cannot be accessed

static

 Value belongs to the class and not an instance of it. If public, it can be accessed without object pointer, just by ClassName.variable 
class ExampleClass
{
	static bool bStaticValue;
	private static bool m_bPrivate; // it is good practice to make it protected/private and have getters/setters instead
}
 
Print(ExampleClass.bStaticValue);	// works
ExampleClass.bStaticValue = true;	// works
 
ExampleClass classInstance = new ExampleClass();
Print(classInstance.bStaticValue);	// works
classInstance.bStaticValue = true;	// works

autoptr

 Modifier for class/pointer values. Pointed object will be automatically destroyed upon end of variable lifetime (end of scope, or deletion of class, that contain it).

ref

 Strong reference.


Code Keywords

new

 Creates an instance of the provided class. 
class ExampleClass
{
}
 
ExampleClass classInstance = new ExampleClass();

class ExampleClass
{
	void ExampleClass(int myValue) // a method named from the class is the constructor
	{
		Print(myValue);
	}
}
 
ExampleClass classInstance = new ExampleClass(5); // needs Constructor-defined arguments

delete

 Deletes an object and sets all its references to null.
⚠
It is not possible to delete an object if there is an external reference to it, like an array.
class ExampleClass
{
	void Method()
	{
		ReferencedClass obj;
		if (!obj)
			Print("obj is null");

		obj = new ReferencedClass();
		if (obj)
			Print("obj is not null");

		delete obj;
		if (!obj)
			Print("obj is null");

		// everything was fine

		obj = new ReferencedClass();
		if (obj)
			Print("obj is not null");

		array<ref ReferencedClass> list = {};
		list.Insert(obj);

		delete obj; // throws a VM Exception
	};
};

thread

 Creates a thread (parallel processing) from a method. Returns the thread, not the method value.

null

 A null value.

this

 Refers to the method's object itself. 
class ExampleClass
{
	void MethodA()
	{
		this.MethodB();
	}

	void MethodB()
	{
		Print("It works");
	}
}

super

 Refers to the parent class for the requested variable/function. 
class Gen1
{
	void Method()
	{
		Print("Gen1 method");
	}
}

class Gen2 : Gen1
{
	void Method()
	{
		Print("Gen2 method");
	}
}

class Gen3 : Gen2
{
	void Method()
	{
		super.Method(); // prints "Gen2 method"
	}
}


Code Flow Keywords

if

 verifies a boolean condition. If the condition is true then the code is executed. 
void Method(int value = 0)
{
	if (value > 50)
	{
		Print("value is > 50");
	}
}

else

 optional, declares code to be executed if the if condition is not met 
void Method(int value = 0)
{
	if (value > 50)
	{
		Print("value is > 50");
	}
	else
	{
		Print("value is <= 50");
	}
}

for

 processes code while the provided condition is met. The syntax is: 
for (initialisation; loopCondition; completionCode)
{
	// code here
}

void MethodA(notnull array<string> words)
{
	for (int i = 0; i < words.Count(); i++)
	{
		Print(words[i]);
	}
}

void MethodB(notnull array<string> words)
{
	int i = 0;
	for (; i < words.Count(); i++) // initialisation is optional
	{
		Print(words[i]);
	}
}

void MethodC(notnull array<string> words)
{
	for (int i = 0; i < words.Count();) // so is completionCode
	{
		Print(words[i]);
		i++;
	}
}

foreach

 processes code for each element of an iterable object (e.g an array). Iteration separator is:. 
// array example
void Method(notnull array<string> words)
{
	foreach (string word : words)
	{
		Print(word);
	}

	foreach (string word, int index : words)
	{
		PrintFormat("word #%1 is %2", index, word);
	}
}

// map example
void Method(notnull map<string, int> data)
{
	foreach (string key, int value : data)
	{
		PrintFormat("Key %1's value is %2", key, value);
	}
}

while

 processes code while condition is met. Beware, as it can lock the program on wrong conditions! 
void Method(array<string> words)
{
	int i = 0;
	while (i < words.Count())
	{
		Print(words[i]);
		i++; // do not forget it!
	}
}

switch

 switches the code to execute depending on the condition 
void Method(string word)
{
	switch (word)
	{
		case "Hello":
			Print("it's Hello");
			break;

		case "there":
			Print("it's there");
			break;

		default:
			Print("it's not interesting.");
			break;
	}
}

return

 stops the code flow and returns the provided value. No value needs to be provided for void methods.
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