Delphi7，创建许多具有相同属性的控件

Question

I am new to Delphi.

I would like to make an application in which will create a number of Buttons. Declaring an array of Tbuttons and create the buttons 1 by 1 is not very satisfying, because it is confusing and takes a lot of time. Using the Command For is also unsatisfying, because i won't be able to change some of button's properties, if needed, for example their position.

So i decided to declare a procedure in TForm1 Class, which creates the buttons based on what properties I send to the procedure. But for some reason it is not working (There aren't any syntax Errors):

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)                       //Declaring the procedure
  procedure CreateButton(Button: TButton; L: Integer; T: Integer); 
  procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  B1, B2: TForm1;         //Declaring controls
implementation

{$R *.dfm}

procedure TForm1.CreateButton(Button: TButton; L: Integer; T: Integer);
begin
  Button:= TButton.Create(Self);
  Button.Parent:= Self;
  Button.Width:= 100; Button.Height:= 50;
  Button.Left:= L; Button.Top:= T;
end;


procedure TForm1.FormCreate(Sender: TObject);
Var
  Button1, Button2: TButton;
begin
  B1.CreateButton(Button1, 100, 50);           //Sending properties
  B2.CreateButton(Button2, 200, 40);           //Sending properties
end;

end.

Answer 1

AS: during the communication with topic starters answer grown too. The total outcome is like http://pastebin.ca/2426760

 procedure TForm1.CreateButton(VAR Button: TButton; CONST L: Integer; CONST T: Integer);

That is of basics of Pascal language how to pass parameters to procedures/functions.

http://docwiki.embarcadero.com/RADStudio/XE4/en/Parameters_(Delphi)

Actually, I don't think there is any problem with the parameters
Button = nil, which means the values of "Button1" and "Button2" are not sent, however

http://pastebin.ca/2427238

---

Kudoes to Bill for spotting this. Using separate properties to position your controls is both inefficient and prone to copy-paste errors.

• http://docwiki.embarcadero.com/Libraries/XE3/en/Vcl.Controls.TControl.SetBounds
• http://docwiki.embarcadero.com/CodeExamples/XE3/en/BoundsRect_(Delphi)

Using the 2nd link:

procedure TForm1.CreateButton(out Button: TButton; const L: Integer; const T: Integer);
begin
  Button:= TButton.Create(Self);
  Button.Parent:= Self;
  Button.SetBounds( L, T, 100, 50); 
end;

---

Actually what do you do with pointers to newly created buttons ? In your code you just loose them!

procedure TForm1.FormCreate(Sender: TObject);
Var
  Button1, Button2: TButton;
begin
...
end;

In this your code those pointers would be just lost! If you do need those values - pass them outside of the procedure. If you do not - do not ask for them - http://en.wikipedia.org/wiki/YAGNI http://en.wikipedia.org/wiki/KISS_principle

Procedure TForm1.CreateButton(const L, T: Integer);
begin
  With TButton.Create(Self) do begin
       Parent := Self;
       SetBounds( L, T, 100, 50); 
       Caption := 'Caption at ' + IntToStr(T);
       Name := 'Name at ' + IntToStr(L);
  End; 
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  B1.CreateButton( 100, 50);           //Sending properties
  B2.CreateButton( 200, 40);           //Sending properties
end;

---

Now to those B1, B2...

You claim that you want 2 buttons on the form, but you code shows you try to make THREE FORMS and one button on the 2nd form and one button on the 3rd form. So what do you really want ??? And do you check that B1 and B2 forms were created befoe tryign to add buttons to them ?

Perhaps you really wanted

procedure TForm1.FormCreate(Sender: TObject);
begin
  SELF.CreateButton( 100, 50);           //Sending properties
  SELF.CreateButton( 200, 40);           //Sending properties
end;

---

Then to go with DRY principle and to keep all the variables in one place.

http://docwiki.embarcadero.com/Libraries/XE2/en/System.Types.TPoint

Procedure TForm1.CreateButtons(const a: array of TPoint);
Var p: TPoint;
Begin
    for p in a do
        CreateButton( p.x, p.y );
End;

type TPointDynArray = array of TPoint;

procedure TForm1.FormCreate(Sender: TObject);
begin
   CreateButtons( TPointDynArray.Create(
       Point( 100,50 ), Point(200, 40) ) );
end;

Kudos to Delphi array initialization

Later you can always add more coordinates to an array and keep it consistent. Well, to bring down this to Delphi 7 abilities that would - somewhat redundantly - be coded like

const BtnCnt = 2;
      BtnLocations : array [1..BtnCnt] of TSize = (
         ( cx: 100, cy: 50 ), ( cx: 200, cy: 40 ) 
      );

Procedure TForm1.CreateButtons(const a: array of TSize);
Var i: integer;
Begin
    for i := Low(a) to High(a) do
        with a[i] do
             CreateButton( cx, cy );
End;

procedure TForm1.FormCreate(Sender: TObject);
begin
   CreateButtons( BtnLocations );
end;

But while Delphi 5 and Dephi 7 were great releases, they are very outdated. I definitely suggest you either upgradeing to Delphi XE or more recent, or side-stepping to CodeTyphon

---

TForm1 = class(TForm)                       //Declaring the procedure
    procedure CreateButton(Button: TButton; L: Integer; T: Integer); 

Declaring that one-purpose procedure in PUBLISHED section of the form class is also not a very good style. You'd better declare them in PRIVATE section. Adhering to "least visibility" would help you to make interdependencies controllable. Otherwise in a year your program would become a spaghetti mess, where you just cannot change anything without ruining everything else. I am workign on a project with 10+ years of history now and i see the consequences of "everything is public" very clear. It is a great pain!