Normally I try to write applications on the DataWindow or Appeon but every
now and then I get a question that makes me sit back and say, "Huh?"
In this case the question concerns the PostOpen event. I've seen that event
named different things: ue_post_open, postOpen, post_open, ue_postOpen, etc.
It has, as far as I can see, always had post and open in the name of the
event. Further, just about every framework that I've ever seen has had that
event in the base window.
The question that I was asked was, "Why is that event there?"
The programmer wanted to know why there was code in the post open and why was
it not just put at the end of the open event? At first I was really confused
by the question. It was like he was asking me why do we have arrays? I just
couldn't imagine not knowing the answer.
Then it occurred to me that I learned the answer to that question from a ... (more)
The following article is an excerpt from Rik's upcoming book, ‘Mobile
Application Development using PowerBuilder and Appeon'
I am here to tell you it's true. You can write iPad applications in
PowerBuilder. I'm sure that you are waiting for the other shoe to drop but
ladies and gentlemen, there is no other shoe. It is simply the truth. You can
write iPad applications in PowerBuilder.
Those of you who have iPads, have you ever seen an MDI application running on
an iPad? No? Neither had I. That is until I took a PowerBuilder application
and, using Appeon, deployed to my iPad and ra... (more)
Every programmer knows about the IF command. It's pretty much a fundamental
part of the syntax of every computer language that has ever existed. I don't
need to explain how it works.
The DataWindow can't use the IF command though. It does, however, support an
IF(expression, TRUE, FALSE)
In its simplest form this means that if the expression evaluates to TRUE,
then whatever statement you supply for the TRUE part is executed. If not then
the FALSE part is.
Let's begin with a simple example. Let's create a DataWindow that will show
employee information. Here is the SQ... (more)
In the October issue of PBDJ we worked on the design for our mail server on
Jaguar. This is more accurately called an MDA, or Mail Delivery Agent. What
we're writing isn't the application that will receive raw messages from the
Internet, parse them out, then store them for another application to
download. It in fact does the downloading.
This relationship is beyond the scope of this series, but it needs to be
addressed simply to avoid confusion. What we're considering is something far
closer to a Microsoft Outlook than a SendMail.
So why write a replacement for Microsoft Outlook?... (more)
One of the most useful custom objects that I've ever written is my
master_detail object. It holds a prominent place in my toolkit. This article
will take you through the steps of how to write one and in the process
de-mystify the object.
First we want something that looks like Figure 1. Selecting a row in the top
DataWindow will display the details in the bottom. I'm sure that you've seen
this kind of DataWindow and you've probably written many of them. The key
here is not to tell you how to write this but how to simplify every one that
you will write in the future. For our exam... (more)