inheritance

[sancho1980]

Hi!
I have made the following 3 definitions in one unit:

type
TEntry = class
private
FTarget: WideString;
FSource: WideString;
public
property Source: WideString read FSource write FSource;
property Target: WideString read FTarget write FTarget;
end;

type
PEntry = ^TEntry;

type
TVocabularyList = class(TList)
private
public
function LoadFromFile(FileName: String): Boolean;
end;

Now I'm trying to use them in another but the inheritance from TList in TVocabularyList doesn't seem to work properly, at least the following assignment does not compile, does anybody have a clue why?

var
TMemoQuestion: TMemo;
...
...
TMemoQuestion.Text := TMemoQuestion.Text + (^((PEntry)VocabularyList.Items)).Source;

Cheers,
Martin

 

[Griffyn]

You must instantiate your classes in order to use them.

var
  MemoQuestion: TMemo;
  MyList: TVocabularyList;
begin
  MemoQuestion := TMemo.Create;  // instantiate
  MyList := TVocabularyList.Create;  // instantiate
  MemoQuestion.Text := MemoQuestion.Text + MyList.Items[i].Source;
  ...
  MyList.Free;  // delete object and free memory
  MemoQuestion.Free;
end;