How to declare two inter-linked classes?
See Forward Declarations and Mutually Dependent Classes
documentation.
type (* start type section - one unified section "to rule them all" *)
TAsyncPopulator = class; (* forward declaration *)
TThreadPopulator = class(TThread)
private
_owner:TASyncPopulator;
end;
TAsyncPopulator = class (* final declaration - WITHIN that very section where forward declaration was made *)
private
_updater: TThreadPopulator;
end;
Use the source, Luke! Your Delphi installation has full VCL and RTL sources for you to read and watch and learn. And it uses this template a lot. Every time when you ask yourself "how I could do it", just think along "how did Borland do it" and pretty chance that you can already get a ready-made example in Delphi-provided sources.
Use this before any class definition. Forward class works in Delphi 2010. I don't know witch version of delphi you have but it's the only solution I can think off.
type
TAsyncPopulator = Class;
Hope I helped