I was wondering the same thing. tiOPF uses RTTI and published
properties. Cesar did mentioned that he uses is own runtime type
registration/process and not standard RTTI. Not sure what the benefit
of that would be?
The problem is that simple types dont have all necessary information, so
I use for use only for Fields, and the BO keed with simples type properties.
All next problems dont exist using this way.
* how do save a property String = '' ?
o EmptyStr or NULL?
* and how about numeric types when zero
o save 0 or NULL?
* With VTF I only need this:
o if not Object.Member[I].IsNull then
* if a have a object with 20 properties, do you send all for
database? I send only the modified, and if no one was modified i
dont send nothing
o if Object.Member[I].State.Modified then
* Notification: when a property is changed, the Field notifies the
object and object notifies objectlist, so if I call a
Save(ObjectList) and the ObjectList.State.Modified = False, I know
that is no object to persist
* as TValueType implements ISubject, is very easy to link Visual
Components, I just need to create a object that implements
observer and Attach
o FNameView:= TEditView.Create(EditName);
o Person.Member['Name'].Attach(FNameView);
TEditView = class(TView, IEditView, IObserver)
private
FEdit: TEdit;
procedure EditChange(Sender: TObject);
function GetEdit: TEdit;
protected
procedure Update(const Sender: IInterface; const NotifyType:
TNotifyType); override
function GetEdit: TEdit;
property Edit: TEdit read GetEdit;
public
constructor Create(const Edit: TEdit); reintroduce; virtual;
end;
{ TEditView }
constructor TEditView.Create(const Edit: TEdit);
begin
inherited Create(Edit); // pass Edit to inherited Control property
FEdit:= Edit;
end;
procedure TEditView.EditChange(Sender: TObject);
begin
(Subject as IStringType).Value:= Edit.Text;
end;
function TEditView.GetEdit: TEdit;
begin
Result:= FEdit;
end;
procedure TEditView.Update(const Sender: IInterface;
const NotifyType: TNotifyType); virtual; abstract;
var
LValue: IStringType;
begin
inherited;
if (Sender <> Self) and Supports(Sender, IStringType, LValue) then
begin
case NotifyType of
ntClear:
Edit.Clear;
ntDetached:
begin
Edit.Clear;
Edit.OnChange:= EditChange;
end;
ntAttached:
begin
Edit.Text:= LValue.Value;
Edit.OnChange:= EditChange;
end;
ntLoaded,
ntChanged:
Edit.Text:= LValue.Value;
end;
end;
end;
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