Find a component by name

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1

I have a string:

var
  vMinhastring : string;
begin
  vMinhastring := 'Edit1';

In my form I have a Tedit Compomente with the name Edit1. How I pass some value to my Edit1, using vMinhastring as the Component name?

  vMinhastring.text := 'batatinha';

I’m trying to do this, but I’m having problems:

contElem := 1;
Rdb1:= TRadioGroup.Create(TabSheet1);
Rdb1.Parent:= TabSheet1;
Rdb1.OnExit := Validacao;
Rdb1.Name:='Rdb'+IntToStr(contElem);
Rdb1.Items.Add('C');

Edit := TMaskEdit.Create(TabSheet1);
Edit.Parent:= TabSheet1;
Edit.Name:='Edit'+IntToStr(contElem);
Edit.Clear;
Edit.EditMask := ('!99;1;');

contElem := 2;
Rdb1:= TRadioGroup.Create(TabSheet1);
Rdb1.Parent:= TabSheet1;
Rdb1.OnExit := Validacao;
Rdb1.Name:='Rdb'+IntToStr(contElem);
Rdb1.Items.Add('C');

Edit := TMaskEdit.Create(TabSheet1);
Edit.Parent:= TabSheet1;
Edit.Name:='Edit'+IntToStr(contElem);
Edit.Clear;
Edit.EditMask := ('!99;1;');

I created a trial:

procedure TFCad_AnaliseDeTendencias.Validacao(Sender: TObject);
var
 name, name2 :string;
 i : integer;
begin
   name := TRadioGroup(Sender).Name;
   name2 := '';
   for i := 1 to Length(name) do
   begin
      if name[i] in ['0'..'9'] then
         name2 := name2 + name[i];
   end;
   name2 := 'Edit'+name2;
   TMaskEdit(FindComponent(name2)).Text := '01'; //Esta dando erro aqui.
end;

Is making a mistake of

Access Violation at address

delphi delphi-7

  • What you need is not Edit1.Text = vMinhastring; ?

  • that’s not what I need.

  • You will also need to specify the type of the component. Ex: 'Edit1' of type 'Tedit'. Having this in m]aos you will work with Typecast and/or RTTI. If you need an example just ask, but if you do a search on Typecast and rtti you will understand what I am saying.

  • So it seems to me that you want to find a control dynamically in the form having only his name, that’s it?

  • That’s right @Pagotti

  • @Victortadashi has some example, using Typecast?

  • @Tiagocasanova took his last edition and no error occurs, a revised!

  • Was any of the answer helpful? Don’t forget to choose one and mark it so it can be used if someone has a similar question!

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3 answers

1


Well, I built a prototype with RTTI that looks better. Follow the code:

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Panel1: TPanel;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    function CriarComponente(AClassType: TClass; AName: String; AParent: TWinControl): TComponent;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

uses
  Rtti;

{$R *.dfm}

{ TForm1 }



procedure TForm1.Button1Click(Sender: TObject);
begin

  CriarComponente(GetClass(Edit1.Text), Edit2.Text, Panel1);

end;



function TForm1.CriarComponente(AClassType: TClass; AName: String; AParent: TWinControl): TComponent;
var
  RttiContext: TRttiContext;
  RttiInstanceType: TRttiInstanceType;
  Value: TValue;
begin

  RttiInstanceType                       := (RttiContext.GetType(AClassType) as TRttiInstanceType);
  Value                                  := RttiInstanceType.GetMethod('Create').Invoke(RttiInstanceType.metaClassType, [self]);
  (Value.AsObject as TWinControl).Parent := AParent;

end;



procedure TForm1.FormCreate(Sender: TObject);
begin
  RegisterClasses([TButton, TForm, TEdit]);
end;

end.

On the program screen, I added 2 edits where you will inform the component type and its name, a button to run, and a panel to be the components Parent.

Obs.: It is necessary to check the classes you can create, ex: RegisterClasses([TButton, TForm, TEdit]);

  • In reality what he asked is not how to create a new component but how to add a text to an existing one just knowing the name

  • @Sorack, you are right

0

Look at this:

procedure TForm13.Button1Click(Sender: TObject);
Var
   tabSheet: TTabSheet;
   AComponent: TComponent;
   aIndex: Integer;
begin
   aIndex:=-1;

   AComponent := FindComponent('TabSheet1');
   if Assigned(AComponent) then
     if AComponent is TTabSheet then
       aIndex := TTabSheet(AComponent).PageIndex; //get the index of the 'TabSheet1'  

   tabSheet := TTabSheet.Create(PageControl1);
   tabSheet.PageControl := PageControl1;
   tabSheet.Caption := 'My TabSheet'+IntToStr(PageControl1.PageCount);
   if aIndex>-1 then
     tabSheet.PageIndex := aIndex; //Set the index of the new TabSheet
end;

0

You can use the function System.Classes.TComponent.FindComponent:

TEdit(FindComponent(vMinhastring)).Text := 'Meu texto';

Findcomponent

Original: Findcomponent Returns the Component in the Components Property array with the name that Matches the string in the Aname Parameter.

Free translation: Findcomponent returns the component in the Component array property with the name that matches the string in the Aname parameter.

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