Pascal - Class inheritance between two different files? - pascal

Question

Say I have two files, characters.pas and ogre.pas. An ogre is a character, but I'm trying to separate the two files for cleanliness sake. In characters.pas I have
unit Characters;
{$mode objfpc}{$H+}
interface
type
TCharacter = class(TOBject)
private
// ...
public
// ...
published
// ...
end;
implementation
// Method bodies
end.
In ogre.pas I have
unit Ogre;
{$mode objfpc}{$H+}
interface
type
TOgre = class(TCharacter)
public
constructor create; override;
end;
implementation
constructor TOgre.create();
begin
// Banana banana banana
end;
end.
Adding a uses block anywhere in either of the .pas files throws an error, which leads me to believe that all classes that rely on inheritance must be in the same file as their parents. Am I missing something?

Answer 1

Yes you miss something: the use section. You have to declare that unit Ogre uses unit Characters:
unit Ogre;
{$mode objfpc}{$H+}
interface
uses
Characters;
type
TOgre = class(TCharacter)
public
constructor create; override;
end;
implementation
constructor TOgre.create();
begin
// Banana banana banana
end;
end.
read more:
unit example #FPC
the use of a second form #FPC wiki
Also note that if you want some fields to be visible from a TCharacter to a TOgre but still not accessible from the main program then you'll have to set their visibility to protected