MVVM in Delphi by John Kouraklis

Author:John Kouraklis
Language: eng
Format: epub
Publisher: Apress, Berkeley, CA

implementation

{ TProSuSubscriber }

procedure TProSuSubscriber.SetUpdateSubscriberMethod(

newMethod: TUpdateSubscriberMethod);

begin

fUpdateMethod:=newMethod;

end;

procedure TProSuSubscriber.UpdateSubscriber(const notifyClass: INotificationClass);

begin

if Assigned(fUpdateMethod) then

fUpdateMethod(notifyClass);

end;

end.

Two-Way Communication (Revisited)

We developed the ProSu framework as a response to the need we identified earlier for the View (MainForm) to receive notifications in addition to its ability to initiate communication with the ViewModel. The observer pattern does exactly this; it allows the View to receive notifications from the InvoiceForm to update the Total Sales figure.

Let’s see how this works. We are going to use a simple form to imitate the functionality of printing an invoice and we will investigate how to make the MainForm update the sales figure. We can find the full code in the POSAppMVVMMainFormTest folder in the book’s files. 1.Add a new form in the POSAppMVVMMainForm project, change the name to TestPrintInvoiceForm, and save it in the Views folder with the name View.TestPrintInvoice.pas.

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