unit uTest;

interface

type
  TSomeFunc = procedure( Value : Integer ) of object;

  classA = class(TObject)
  private
  protected
  public
    procedure TestFunc( AValue : Integer );
  end;

  classB = class(TObject)
  private
    FSomeFunc : TSomeFunc;
  public
    procedure Test;
    constructor Create( Func : TSomeFunc );
  end;

implementation

uses SysUtils, Dialogs;

procedure classA.TestFunc( AValue : Integer );
begin
    ShowMessage( IntToStr(AValue) );
end;

constructor classB.Create( Func : TSomeFunc );
begin
    FSomeFunc := Func;
end;

procedure classB.Test;
begin
    FSomeFunc(  100  );
end;

var A : classA;
    B : classB;
begin
    A := classA.Create;
    B := classB.Create( A.TestFunc );

    B.Test;

    B.Free;
    A.Free;
end.

constructor classB.Create( Func : TSomeFunc );
begin
    inherited Create;
    FSomeFunc := Func;
end;