array [1..4] of TPoint as class property

[FranzB 0]

I want  to  use this class  with an array of TPoint  type. 

 

type  TedgearryPoints = Array [1..4] of TPoint ;
type  TGEORect = class 
.....
private :

Fedges : TedgearryPoints ; 

public : 

.....

property  edges : TedgearryPoints   read  Fedge   write   Fedge;

end;

 

 

but   the code fails  because I  can not assign  data  to  the individual edges 

MyGEORECT.Edges[1]   ,  compiles says "[dcc64 Error] GEOUnit.pas(1303): E2064 Left side cannot be assigned to "

 

 

 

 

 

Edited November 28, 2020 by FranzB

[FPiette 383]

You have to use an indexed property:

 

property Edges[Index : Integer] : TPoint read  GetEdges write SetEdges;

 

And then implement GetEdges and SetEdges:

 

procedure TGeoRect.SetEdges(Index : Integer; Pt : TPoint);

begin

  if (Index < Low(FEdges)) or (Index > High(FEdges)) then

     raise ERangeException.Create('Invlid index');

  FEdges[Index] := Pt;

end;

You may also use a type for the range used for indexing the array.

 

 

GetEdge is similar.

 

 

[FranzB 0]

but this means  :  I have to write  extra  code if I want to assign just one edge  with your solution above  via property  or  if I want to assign all 4 edge  with  one  command 

making the edge variable public:  allows both, but I think from class design this  look not that good 

 

type  TGEORect = class 

private :
.....
public :

edges : TedgearryPoints ; 


end;

Edited November 28, 2020 by FranzB

[FPiette 383]

32 minutes ago, FranzB said:

if I want to assign all 4 edge  with  one  command

I would create an overloaded SetEdges:

 

procedure TGEORect.SetEdges(const AEdges : TEdgeArrayPoints);

begin

    FEdges := AEdges;

end;

 

[Guest]

12 hours ago, FranzB said:

I want  to  use this class  with an array of TPoint  type. 

...

MyGEORECT.Edges[1]   ,  compiles says "[dcc64 Error] GEOUnit.pas(1303): E2064 Left side cannot be assigned to "

try this way:

 

 

unit for Class:

unit uMyGEORectClass;

interface

uses
  System.Types,
  System.SysUtils;

type
  TEdgeArryPoints = array [0 .. 3] of TPoint;

  //
  TGEORect = class
  private
    FMyEdges: TEdgeArryPoints;
    procedure SetFMyEdges(const Value: TEdgeArryPoints);
    function GetFMyEdgesPoints: TArray<TPoint>;
  public
    constructor Create(Aowner: TObject);
    destructor Destroy;
    //
    property MyEdges: TEdgeArryPoints read FMyEdges write SetFMyEdges;
    property MyEdgesPoints: TArray<TPoint> read GetFMyEdgesPoints;
  end;

implementation

{ TGEORect }

constructor TGEORect.Create(Aowner: TObject);
var
  i: integer;
begin
  inherited Create;
  //
  for i         := low(FMyEdges) to high(FMyEdges) do
    FMyEdges[i] := TPoint.Zero;
end;

destructor TGEORect.Destroy;
begin
  inherited Destroy;
end;

function TGEORect.GetFMyEdgesPoints: TArray<TPoint>;
var
  lMyPoint: TPoint;
begin
  for lMyPoint in FMyEdges do
    result := result + [lMyPoint];
end;

procedure TGEORect.SetFMyEdges(const Value: TEdgeArryPoints);
begin
  FMyEdges := Value;
end;

end.

 

Using the new Class:

implementation

{$R *.dfm}

uses
  uMyGEORectClass;

var
  lMyTEdgeArryPoints: TEdgeArryPoints;
  lMyTGEORect       : TGEORect = nil;

procedure TForm1.btn_Creating_PointsClick(Sender: TObject);
var
  i: integer;
begin
  if not(lMyTGEORect = nil) then
  begin
    Randomize; // to Random() below!
    //
    for i                   := low(lMyTEdgeArryPoints) to high(lMyTEdgeArryPoints) do
      lMyTEdgeArryPoints[i] := TPoint.Create(Random(200), Random(400));
    //
    lMyTGEORect.MyEdges := lMyTEdgeArryPoints;
    //
    // lMyTGEORect.MyEdges[0].SetLocation(0,0); works for 1 item!
  end;
end;

procedure TForm1.btn_Showing_PointsClick(Sender: TObject);
var
  lMyPoints: TPoint;
  lText    : string;
  nPoint   : integer;
begin
  if not(lMyTGEORect = nil) then
  begin
    for lMyPoints in lMyTGEORect.MyEdgesPoints do
      lText := lText + Format('[%d,%d]', [lMyPoints.X, lMyPoints.Y]) + ',';
    //
    if lText.EndsWith(',') then
      lText := lText.Remove(lText.Length - 1); // Delete(lText,lText.Length,1);
    //
    ShowMessage(lText);
    //
    // ShowMessage(lMyTGEORect.MyEdges[0].X.ToString + ' - ' + lMyTGEORect.MyEdges[0].Y.ToString);
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  lMyTGEORect := TGEORect.Create(nil);
  //
  btn_Creating_Points.Click;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  if not(lMyTGEORect = nil) then
    lMyTGEORect.Free;
end;

initialization

ReportMemoryLeaksOnShutdown := true;

finalization

end.

 

 

NOTE: im not "builder" ok!

hug

[pmcgee 10]

Just checking ... You can characterise one edge by one TPoint?  or one edge by 4 TPoints?  or does Fedges describe a parallelogram?

Is ok. "GEORect". I get it. (I'm not sure 'edges' is the best name) ... (also ... can't see how to delete posts.)

Edited November 29, 2020 by pmcgee

[Guest]

48 minutes ago, pmcgee said:

Just checking ... You can characterise one edge by one TPoint?  or one edge by 4 TPoints?  or does Fedges describe a parallelogram?

Is ok. "GEORect". I get it. (I'm not sure 'edges' is the best name) ... (also ... can't see how to delete posts.)

// lMyTGEORect.MyEdges[0].SetLocation(0,0); works for 1 item!  = NOT WORKS FOR YOU?

    lMyTGEORect.MyEdges[0].SetLocation(1,1);
    lMyTGEORect.MyEdges[1].SetLocation(2,2);
    lMyTGEORect.MyEdges[2].SetLocation(3,3);
    lMyTGEORect.MyEdges[3].SetLocation(4,4);

 

 

the "names" stay with you! dont worry!

 

if you needs many  "TGEORect" or "MyEdges", you can extende the class to create a List of Objects with this type, you see?

 

for example: I THINK THAT YOU NEED CHANGE SOMETHING YOUR CLASS BASE for better use!

 

a simple way:

uses
  uMyGEORectClass;

var
  lMyTEdgeArryPoints: TEdgeArryPoints;
  lMyTGEORect       : TGEORect = nil;
  //
  lManyTGEORect: array [0 .. 3] of TGEORect;
...
procedure TForm1.FormCreate(Sender: TObject);
var
  i: integer;
begin
  for i := low(lManyTGEORect) to high(lManyTGEORect) do
  begin
    lManyTGEORect[i] := TGEORect.Create(nil);
  end;
...  
end;
...

// you should use:
// lManyTGEORect[ index n ].MyEdges[ index n ]  to access the element

...
procedure TForm1.FormDestroy(Sender: TObject);
var
  i: integer;
begin
  for i := low(lManyTGEORect) to high(lManyTGEORect) do
  begin
    if not(lManyTGEORect[i] = nil) then
      lManyTGEORect[i].Free;
  end;
end;

 

 

 

I think that is not possible "delete" the posts!  

Edited November 29, 2020 by Guest