XE3 Visual LiveBindings: User defined objects

The adapter components TListBindSourceAdapter and TObjectBindSourceAdapter enable LiveBindings with user defined TObjects.

Here is a user defined TObject  for example.

type

  TContact = class

  private

    FFirstName: string

    FLastName: string

  public

    constructor Create overload

    constructor Create(const AFirstName, ALastName: string) overload

    property FirstName: string read FFirstName write FFirstName

    property LastName: string read FLastName write FLastName

  end



  function LoadContacts: TList<TContact>

implementation



function LoadContacts: TList<TContact>

begin

  Result := TObjectList<TContact>.Create

  // TODO: Load data from file

  Result.Add(TContact.Create('Adam', 'Barns'))

  Result.Add(TContact.Create('Chris', 'Decker'))

  Result.Add(TContact.Create('Emma', 'Fisk'))

end

One way to use TListBindSourceAdapter is to instantiate the adapter at run time.  Drop a TAdapterBindSourceAdapter on the form and implement the CreateAdapter event as follows:

mplementation



{$R *.dfm}



uses ContactsUnit, System.Generics.Collections



procedure TForm1.AdapterBindSource1CreateAdapter(Sender: TObject

  var ABindSourceAdapter: TBindSourceAdapter)

begin

  ABindSourceAdapter := TListBindSourceAdapter<TContact>.Create(Self,

    LoadContacts)

endi

In the LiveBindings designer, we won't see the fields for TContact because the TContact type is not known at design time.

Drop a TStringGrid on the form and connection the '*' of AdapterBindSource1 to StringGrid1.

A navigator can be added by right clicking AdapterBindSource1 and choosing "Add Navigator".

The grid is populated when the application is run:

A TDataGeneratorAdapter can be used to provide some fields to use at design time.  Add fields with the same name as the properties in TContact.  Set AdapterBindSource1.Adapter to DataGeneratorAdapter1.

The form shows sample data and the LiveBindings designer shows field names.

To show this data at design time, the TDataGeneratorAdapter fields have FieldType: ftString and Generator: LoremIpsum.

The LiveBindings designer can be used to connect fields to controls.

Note that an easy way to create a TLabeledEdit is to right click on FirstName then choose "Link to new control…".

At runtime, the TListBindSourceAdapter will be used instead of DataGeneratorAdapter1 because of the CreateAdapter event.

Another way to use TListBindSourceAdapter is to register a custom component.  Instead of instantiating a TListBindSourceAdapter in the CreateAdapter event, the custom component is dropped from the tool palette.  A TDataGeneratorAdapter is not needed.

The minimal code to for a custom adapter looks like this:

unit ContactsAdapter



interface



  uses ContactsUnit, Data.Bind.ObjectScope, System.Classes, System.Generics.Collections



type



  TContactsAdapter = class(TListBindSourceAdapter<TContact>)

  public

    constructor Create(AOwner: TComponent) override

  end



implementation



{ TContactsAdapter }



constructor TContactsAdapter.Create(AOwner: TComponent)

begin

  inherited Create(AOwner)

  SetList(LoadContacts)

end

To register the custom adapter, you will need to create and register a package which contains the custom adapter component and TContact class.  You will also need and a Register method to register the custom component.

unit ContactsAdapterReg



interface



procedure Register



implementation



uses System.Classes, ContactsAdapter, ContactsAdapter2



procedure Register

begin

  RegisterComponents('Test', [TContactsAdapter])

end



end.

A complete implementation of a custom adapter publishes properties and methods:

  TContactsAdapter2 = class(TListBindSourceAdapter<TContact>)

  public

    constructor Create(AOwner: TComponent) override

  published

    property OnBeforeSetList

    property OnAfterSetList

    property OnListAppend

    property OnListDelete

    property OnListInsert

    property OnCreateItemInstance

    property OnInitItemInstance

    property Options

    property AutoEdit

    property BeforeOpen

    property AfterOpen

    property BeforeClose

    property AfterClose

    property BeforeInsert

    property AfterInsert

    property BeforeEdit

    property AfterEdit

    property BeforePost

    property AfterPost

    property BeforeCancel

    property AfterCancel

    property BeforeDelete

    property AfterDelete

    property BeforeScroll

    property AfterScroll

    property BeforeRefresh

    property AfterRefresh

    property BeforeApplyUpdates

    property AfterApplyUpdates

    property BeforeCancelUpdates

    property AfterCancelUpdates

    property OnDeleteError

    property OnInsertError

    property OnEditError

    property OnPostError

    property OnApplyUpdatesError

    property OnCancelUpdatesError

    property OnApplyUpdates

    property OnCancelUpdates

    property OnHasUpdates

  end

TObjectBindSourceAdapter is used instead of TListBindSourceAdapter to bind to a single object, rather than a list of objects.

TObjectBindSourceAdapter is instantiated like this:

procedure TForm1.AdapterBindSource1CreateAdapter(Sender: TObject

  var ABindSourceAdapter: TBindSourceAdapter)

begin

  ABindSourceAdapter := TObjectBindSourceAdapter<TContact>.Create(Self,

    TContact.Create('Adam', 'Barns'))

end

At run time, there is only a single row of data.

Source forge samples

https://radstudiodemos.svn.sourceforge.net/svnroot/radstudiodemos/branches/RadStudio_XE3/LiveBindings/observers

• ContactsAdapterPackage.dpk

  • Implements a custom TListBindSourceAdapter component

• ListAdapterEventProject.dpr

  • Demonstrates  TAdapterBindSource.CreateAdapter event

• ListAdapterComponentProject.dpr

  • Demonstrates custom TListBindSourceAdapter component

• Project: CppListAdapterEventProject.dpr

  • Cpp project demonstrates  TAdapterBindSource.CreateAdapter event