Global declarations

Functions

Global functions are declared normally, just as in C/C++. The function body must be defined, i.e. it is not possible to declare prototypes, nor is it necessary as the compiler can resolve the function names anyway.

For parameters sent by reference, i.e. with the & modifier it is necessary to specify in which direction the value is passed, in, out, or inout, e.g. &out. If no keyword is used, the compiler assumes the inout modifier. For parameters marked with in, the value is passed in to the function, and for parameters marked with out the value is returned from the function.

Parameters can also be declared as const which prohibits the alteration of their value. It is good practice to declare variables that will not be changed as const, because it makes for more readable code and the compiler is also able to take advantage of it some times. Especially for const &in the compiler is many times able to avoid a copy of the value.

Note that although functions that return types by references can't be declared by scripts you may still see functions like these if the host application defines them. In that case you the returned value may also be used as the target in assignments.

int MyFunction(int a, int b)
{
  return a + b;
}

Variables

Global variables may be declared in the scripts, which will then be shared between all contexts accessing the script module.

The global variables may be initialized by simple expressions that do not require any functions to be called, i.e. the value can be evaluated at compile time.

Variables declared globally like this are accessible from all functions. The value of the variables are initialized at compile time and any changes are maintained between calls. If a global variable holds a memory resource, e.g. a string, its memory is released when the module is discarded or the script engine is reset.

int MyValue = 0;
const bits Flag1 = 0x01;

Classes

In AngelScript the script writer may declare script classes. The syntax is similar to that of C++, except the public, protected, and private keywords are not available, and currently there is no support for inheritance. All the class methods must be declared with their implementation, like in Java.

The default constructor and destructor are not needed, unless specific logic is wanted. AngelScript will take care of the proper initialization of members upon construction, and releasing members upon destruction.

With classes the script writer can declare new data types that hold groups of variables and methods to manipulate them.

// The class declaration
class MyClass
{
  // The default constructor
  MyClass()
  {
    this.a = 0;
  }

  // Destructor
  ~MyClass()
  {
  }

  // Another constructor
  MyClass(int a)
  {
    this.a = a;
  }

  // A class method
  void DoSomething()
  {
    this.a *= 2;
  }

  // A class property
  int a;
}

Note, that since AngelScript uses automatic memory management, it can be difficult to know exactly when the destructor is called, so you shouldn't rely on the destructor being called at a specific moment. AngelScript will also call the destructor only once, even if the object is resurrected by adding a reference to it while executing the destructor.

Interfaces

An interface works like a contract, the classes that implements an interface are guaranteed to implement the methods declared in the interface. This allows for the use of polymorphism, in that a function can specify that it wants an object handle to an object that implements a certain interface. The function can then call the methods on this interface without having to know what the exact type of the object that is working with.

// The interface declaration
interface MyInterface
{
  void DoSomething();
}

// A class that implements the interface MyInterface
class MyClass : MyInterface
{
  void DoSomething()
  {
    // Do something
  }
}

A class can implement multiple interfaces; Simply list all the interfaces separated by a comma.

Imports

Sometimes it may be useful to load script modules dynamically without having to recompile the main script, but still let the modules interact with each other. In that case the script may import functions from another module. This declaration is written using the import keyword, followed by the function signature, and then specifying which module to import from.

This allows the script to be compiled using these imported functions, without them actually being available at compile time. The application can then bind the functions at a later time, and even unbind them again.

If a script is calling an imported function that has not yet been bound the script will be aborted with a script exception.

import void MyFunction(int a, int b) from "Another module";