Delphi XE2 and LiveBindings between controls

Question

Is it possible to do LiveBinding between controls, i.e. take 2 edit boxes and get the result of adding their contents together into a label. I'm sure it is, I just don't know where to start

Thanks

Answer 1

Have a look at the samples. SVN repository URL: https://radstudiodemos.svn.sourceforge.net/svnroot/radstudiodemos/branches/RadStudio_XE2/LiveBindings

An example:

----- Unit1.dfm -----

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 286
  ClientWidth = 426
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Label1: TLabel
    Left = 8
    Top = 62
    Width = 48
    Height = 13
    Caption = 'Edit1Edit2'
  end
  object Edit1: TEdit
    Left = 8
    Top = 8
    Width = 121
    Height = 21
    TabOrder = 0
    Text = 'Edit1'
    OnChange = EditChange
  end
  object Edit2: TEdit
    Left = 8
    Top = 35
    Width = 121
    Height = 21
    TabOrder = 1
    Text = 'Edit2'
    OnChange = EditChange
  end
  object BindingsList1: TBindingsList
    Methods = <>
    OutputConverters = <>
    UseAppManager = True
    Left = 20
    Top = 5
    object BindExpressionLabel11: TBindExpression
      Category = 'Binding Expressions'
      ControlComponent = Label1
      SourceComponent = BindScope1
      SourceExpression = 'Edit1.Text + Edit2.Text'
      ControlExpression = 'Caption'
      NotifyOutputs = False
      Direction = dirSourceToControl
    end
  end
  object BindScope1: TBindScope
    Left = 192
    Top = 16
  end
end

----- Unit1.pas -----

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Data.Bind.EngExt, Vcl.Bind.DBEngExt,
  System.Rtti, System.Bindings.Outputs, Vcl.Bind.Editors, Data.Bind.Components,
  Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Label1: TLabel;
    BindingsList1: TBindingsList;
    BindExpressionLabel11: TBindExpression;
    BindScope1: TBindScope;
    procedure EditChange(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses
  System.Bindings.Helper;

procedure TForm1.EditChange(Sender: TObject);
begin
  TBindings.Notify(Sender, 'Text');
end;

end.

---

How to use the IDE designer to produce the result:

• put two edits (Edit1, Edit2), a label (Label1) and a TBindScope (BindScope1) on your form (Form1).
• create an event handler for both edits' OnChange event (EditChange).
• select Label1, expand the drop-down of LiveBindings property, select 'New Live Binding...', select TBindExpression
• edit properties of the newly created BindExpressionLabel11: assign Caption to ControlExpression, BindScope1 to SourceComponent, Edit1.Text + Edit2.Text to SourceExpression

Answer 2

The sample project at the (Default) location of:

C:\Users\Public\Documents\RAD Studio\9.0\Samples\Delphi\LiveBinding\Components\bindexpression\fmx\BindExpressionSampleProject.dproj

does precisely that.

Answer 3

You don't need to TBindScope to bind components together. Say you have edit1 and edit2 on the form. If you set edit2 BindingSource to edit1 it will be link to changes to edit1