Generate compiler error if property is not set

Question

I want to be able to create a compiler error/warning if a certain property in my object is not set. Let's say I have the following class:

interface

type
  TBarkevent = procedure (Bark : String) of object;

  TDog = class
  private
    FOnBark : TBarkevent;
    procedure SetBark(const Value: TBarkevent);
    function GetBark: TBarkEvent;
  public
    procedure Bark;
    property OnBark : TBarkEvent read GetBark write SetBark;
    constructor Create;
  end;

implementation

{ TDog }

procedure TDog.Bark;
begin
  if Assigned(OnBark) then
    OnBark('Woof!')
end;

constructor TDog.Create;
begin
end;

function TDog.GetBark: TBarkEvent;
begin
  Result := FOnBark;
end;

procedure TDog.SetBark(const Value: TBarkevent);
begin
  FOnBark := Value;
end;

I make use of the TDog class in another unit like this:

var
  Dog : TDog;
begin
  Dog := TDog.Create;
  Dog.OnBark := DogBark;
  Dog.Bark;

Now, once the Bark() procedure is called, the OnBark event is triggered.

My Question:

Is it possible for me to make it mandatory to specify the OnBark property, so that a compiler error/warning is emitted if the event is not set?

Answer 1

Define your class as:

TDog = class
private
  FOnBark : TBarkevent;
  procedure SetBark(const Value: TBarkevent);
  function GetBark: TBarkEvent;
public
  procedure Bark;
  property OnBark : TBarkEvent read GetBark write SetBark;
  constructor Create(Bark : TBarkEvent);
end;

That way, you can't instantiate a TDog object without specifying an event. If you try, you'll get a compiler error.