5.1 Class definitions

The prototype declaration of a class is as follows :

_________________________________________________________________________________________________________ Class types
-------------class----------------------------------end-----------
-packed -| heritage-|------component list----|
-class visibility specifier

-- - - - ----------------------------------
heritage ( class type identifier )

-- component list-|-----------------|------------------------------
--field-definition--- ----method definition-----
--property definition--|

-- field definition-identifier list-:-type -;------------------------------

-- method definition-------------function header-----;--
|-class -| -procedure header| |
------constructor header------|
------desctuctor header------|
----------------------------------------------------------------
-----virtual -|----------------; -| -call modifiers ;-|
| -; -abstract-- |
|--------override----------|
-message --|integer constant---
-string constant-

-- class visibility specifier-|- private------------------------------------
|protected -|
|--public---|
- published--|
___________________________________________________________________

As many private, protected, published and public blocks as needed can be repeated. Methods are normal function or procedure declarations. As can be seen, the declaration of a class is almost identical to the declaration of an object. The real difference between objects and classes is in the way they are created (see further in this chapter). The visibility of the different sections is as follows:

Private: All fields and methods that are in a private block, can only be accessed in the module (i.e. unit) that contains the class definition. They can be accessed from inside the classes’ methods or from outside them (e.g. from other classes’ methods)
Protected: Is the same as Private, except that the members of a Protected section are also accessible to descendent types, even if they are implemented in other modules.
Public: sections are always accessible.
Published: Is the same as a Public section, but the compiler generates also type information that is needed for automatic streaming of these classes. Fields defined in a published section must be of class type. Array peroperties cannot be in a published section.

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