Custom class adding itself to array of that class

[TomTom]

Hi. I have this :

Code: Pascal  [Select][+][-]

1. type
2.  
3.   EAreaType = (atVillage, atTown, atCity, atDungeon, atSite, atEvent);
4.  
5.   { TMapArea }
6.  
7.   TMapArea = class
8.     FArea : TRect;
9.     FType : EAreaType;
10.     public
11.       property Area : TRect read FArea write FArea;
12.       property AreaType : EAreaType read FType write FType;
13.  
14.       constructor Create(aList: array of TMapArea; aType: EAreaType; aRect: TRect);
15.   overload;  

Code: Pascal  [Select][+][-]

1. constructor TMapArea.Create(aList: array of TMapArea; aType: EAreaType;
2.   aRect: TRect);
3. begin
4.   self.FType := aType;
5.   self.FArea := aRect;
6.   SetLength(aList, (Length(aList) + 1));
7.   aList[Length(aList)]:=self;
8. end;

I would like to add new objects of that class to be added to pointed array. This gives me type mismatch and I can't figure out why. Ofcourse I can add it later in the code but not in Create . I'm missing something but don't know what.

[alpine]

Shouldn't it be that way (-1)?

Code: Pascal  [Select][+][-]

1. aList[Length(aList)-1]:=Self;

[bytebites]

Code: Pascal  [Select][+][-]

1. constructor TMapArea.Create(aList: array of TMapArea; aType: EAreaType;
2.   aRect: TRect);

The reason to type mismatch is that aList is open array not dynamic array.

[Zvoni]

Independent of the Answers above: Wouldn't "aList" be lost, once the constructor finishes?

[Thaddy]

Yes. It needs to be var (or maybe out).
Another option is to have a class constructor but that needs some internal management.

[howardpc]

It needs to be written thus  to compile:

Code: Pascal  [Select][+][-]

1. type
2.  
3.   EAreaType = (atVillage, atTown, atCity, atDungeon, atSite, atEvent);
4.  
5.   TMapArea = class;
6.  
7.   TMapAreaArray = array of TMapArea;
8.  
9.   TMapArea = class(TObject)
10.   private
11.     FArea : TRect;
12.     FType : EAreaType;
13.   public
14.     constructor Create(var aList: TMapAreaArray; aType: EAreaType; aRect: TRect); //overload;
15.     property Area : TRect read FArea write FArea;
16.     property AreaType : EAreaType read FType write FType;
17.   end;
18.  
19.   constructor TMapArea.Create(var aList: TMapAreaArray; aType: EAreaType; aRect: TRect);
20.   begin
21.     FType := aType;
22.     FArea := aRect;
23.     SetLength(aList, (Length(aList) + 1));
24.     aList[High(aList)] := Self;
25.   end;

[TomTom]

Thank You howrdpc .