Interfaces

Interface <name> [Extends <name>]
  <Method[.<type>]()>
  ...
EndInterface

Interfaces are used to access Object Oriented modules, such as COM (Component Object Model) or DirectX dynamic libraries (DLL). These types of libraries are becoming more and more common in Windows, and through the use of interfaces, the ability to access these modules easily (and without any performance hit) is realized. It also introduces the necessary basis for Object Oriented programming within PureBasic, but the use of interfaces requires some advanced knowledge. Most of the standard Windows interfaces have already been implemented within a resident file and this allows direct use of these objects.

The optional Extends parameter may be used to extend another interface with new functions (Theses functions are commonly called 'methods' in Object Oriented (OO) languages such as C++ or Java). All functions contained within the extended interface are then made available within the new interface and will be placed before the new functions. This is useful in order to do basic inheritance of objects.

Arrays can be passed as parameters using the Array keyword, lists using the List keyword and maps using the Map keyword.

A return type may be defined in the interface declaration by adding the type after the method.

SizeOf may be used with Interfaces in order to get the size of the interface and OffsetOf may be used to retrieve the index of the specified function.

The pseudotypes may be used for the parameters of the functions, but not for the return value.

Note: The concept of objects, and the capability provided within PureBasic for their use, has been developed for, and mainly targeted towards, experienced programmers. However, an understanding of these concepts and capabilities are in no way a prerequisite for creating professional software or games.

Example: Basic example of object call

  ; In order to access an external object (within a DLL for example),
  ; the objects' interface must first be declared:

  Interface MyObject
    Move(x,y)
    MoveF(x.f,y.f)
    Destroy()
  EndInterface
  
  ; CreateObject is the function which creates the object, from the DLL,
  ; whose interface has just been defined.
  ; Create the first object...
  ;
  Object1.MyObject = MyCreateObject()
  
  ; And the second one.
  ;
  Object2.MyObject = MyCreateObject()
  
  ; Then the functions which have just been defined, may 
  ; be used, in order to act upon the desired object.
  ;
  Object1\Move(10, 20)
  Object1\Destroy()
  
  Object2\MoveF(10.5, 20.1)
  Object2\Destroy()

Example: Example with 'Extends'

  ; Define a basic Cube interface object.
  ;
  Interface Cube
    GetPosition()
    SetPosition(x)
    GetWidth()
    SetWidth(Width)
  EndInterface
  
  Interface ColoredCube Extends Cube
    GetColor()
    SetColor(Color)
  EndInterface
  
  Interface TexturedCube Extends Cube
    GetTexture()
    SetTexture(TextureID)
  EndInterface
  
  ; The interfaces for 3 different objects have now been defined, these objects include:
  ;
  ; - 'Cube' which has the: Get/SetPosition() and Get/SetWidth() functions.
  ; - 'ColoredCube' which has the: Get/SetPosition(), Get/SetWidth() and Get/SetColor() functions.
  ; - 'TexturedCube' which has the: Get/SetPosition(), Get/SetWidth() and Get/SetTexture() functions.
  ;