Delphi XE2 and LiveBindings between controls - delphi

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