Store and read the Objects in/from TObjectList - oop

Question

TPoint = Class
private
FX: double;
FY: double;
public
constructor Create(X,Y:double);
destructor Destroy; override;
property X: double read FX write FX;
property Y: double read FY write FY;
end;
TLine= Class(TObjectList)
private
function GetItem(Index: Integer): TPoint;
procedure SetItem(Index: Integer; const Value: TPoint);
public
constructor Create;
destructor Destroy; override;
procedure Add(APoint:TPoint);
property Items[Index: Integer]: TPoint read GetItem write SetItem; default;
end;
TLineStorage= Class(TObjectList)
private
function GetItem(Index: Integer): TLine;
procedure SetItem(Index: Integer; const Value: TLine);
public
constructor Create;
destructor Destroy; override;
procedure Add(ALinie:TLine);
property Items[Index: Integer]: TLine read GetItem write SetItem; default;
end;
TStorage= Class(TObjectList)
private
function GetItem(Index: Integer): TLineStorage;
procedure SetItem(Index: Integer; const Value: TLineStorage);
public
constructor Create;
destructor Destroy; override;
procedure Add(ALinieStorage:TLineStorage);
property Items[Index: Integer]: TLineStorage read GetItem write SetItem; default;
end;
TMeasuring= Class
private
FLine: TLine;
FLineStorage: TLineStorage;
FStorage: TStorage;
public
constructor Create;
destructor Destroy; override;
procedure DoMeasuring;
end;
{ TMeasuring }
constructor TMeasuring.Create;
begin
inherited;
FLineStorage:= TLineStorage.Create;
FLineStorage.OwnsObjects:= true;
FLine:= TLine.Create;
FLine.OwnsObjects:= true;
FStorage:= TStorage.Create;
FStorage.OwnsObjects:= true;
end;
destructor TMeasuring.Destroy;
begin
FLineStorage.Free;
FLine.Free;
FStorage.Free;
inherited;
end;
procedure TMeasuring.DoMeasuring;
var i,j: integer; X,Y: double;
begin
for j:= 0 to 2 do // Lines
begin
for i:= 0 to 5 do // Points
begin
X:= 1+ random(100);
Y:= 1+ random(100);
FLine.Add(TPoint.Create(X,Y)); // 1... X Points
end;
FLineStorage.Add(FLine); // 3 x Linie
FLine.Clear; // for new measuring !!! if not-> it works !!!
end;
FStorage.Add(FLineStorage); // save
for i:= 0 to FStorage.Count-1 do
begin
X:= FStorage.Items[i].Items[i].Items[i].X; // it doesn't work...
ShowMessage(FloatToStr(X));
end;
end;
I work with Delphi 7 and I try to store and display the results of a measurement. But if I try to read the X / Y points I get a range exception. If I comment FLine.Clear; off, it works. How do you get around this problem?
In addition, the program comes out with a message that relates to the storage.
All of the GetItem- functions look like:
function TLine.GetItem(Index: Integer): TPoint;
begin
result:= TPoint(inherited Items[Index]);
end;
Thank you in advance.

Answer 1

You should create your FLine in DoMeasuring
procedure TMeasuring.DoMeasuring;
var i,j: integer; X,Y: double;
FLine : TLine;
begin
for j:= 0 to 2 do // Lines
begin
FLine := TLine.create;
for i:= 0 to 5 do // Points
begin
X:= 1+ random(100);
Y:= 1+ random(100);
FLine.Add(TPoint.Create(X,Y)); // 1... X Points
end;
FLineStorage.Add(FLine); // 3 x Linie
//FLine.Clear; // for new measuring !!! if not-> it works !!!
end;
FStorage.Add(FLineStorage); // save
for i:= 0 to FStorage.Count-1 do
begin
X:= FStorage.Items[i].Items[i].Items[i].X; // it doesn't work...
ShowMessage(FloatToStr(X));
end;
end;