Bastiaan en Lily's blog

I forgot to put this on ages ago. The file for part 5 of the tutorial contains the end result. I made this so long ago I'm crossing my fingers that is still works:) but back by popular demand:

www.basenlily.me/downloads/part_5.zip

I've been way to busy lately to do any personal posts however today there was a topic on the Omnis discussion list about subwindows and communication between them and their parent windows that made me want to write a little something about it. The topic has come up many times in the past and since it is something I've done a lot with it seemed like a good idea to do a little sample library and add some explanation.

Subwindows are basically windows that are contained within another window. They are Omnis Studio's answer to be able to reuse visual components in multiple places in your application. This can be anything from a subwindow containing a single component/field to a subwindow that allows you to enter an entire record consisting of a dozen entry fields.

The problem herein is how to properly communicate between the subwindow and its parent window.
Object Orientation states that any object should not assume or directly influence another object that contains/uses it. That is the only way to guarantee an object can be reused in multiple places without any restrictions in the behavior of the object that uses it. A subwindow and it's parent however always have a symbiotic relationship in one form or another and some measure of communication between them is required. The parent window communicating with the subwindow is easy as this is simply done through public methods, but the subwindow (as it interacts directly with the user) communicating back to the parent, now their lies the problem.

Some months back there was a discussion on the Omnis lists on how to navigate lists in Omnis Studio effectively. That discussion lead to some interesting discussion given by several people and I've been wanting to summize them on my blog for some time but never got around to it. Even today I don't have time to do a proper writeup but since I just wrote a routine I wanted to share I've decided to do a quick post about these.

I specifically thank Kelly Burgess who gave some great tips on this subject

Every since the whole discussion about object variables and object references in Studio came up this has been linguring in my mind so before I continue with my discussion on a way to use object variables in Omnis I felt compelled to do some ranting :)

I can't be certain but I imagine this discussion lies at the heart of the decision making of how Omnis originally implemented their object model and what direction they took it in.

As I was bragging about this on the Omnis list let's start doing a writeup about this. This will be a multipart writeup on object memory management in Omnis Studio 4 using object references.

This part we'll look at a simple retain/release object base class that allows us to track a single instance of an object that is being used by different parts of the system. It is a widely used model though my primary inspiration has been the use of it in Cocoa.
For the second part we'll look at implementing a copying scheme for our objects.
For the third part we'll look at auto releasing objects, why we need to do this and how we can implement this in Omnis.
The final part we'll look into tracking retains and releases in order to find memory leaks (not just leaks happening but finding the source).

I've placed my old Omnis tutorials back on this blog. They where originally posted on www.omniscentral.com. You can find them by clicking Omnis in the navigation on the right side of this site.

Note that these are already over a year old and I simply copy/pasted them over from my original transcripts. I will go through them at some point and clean them up a little so they show correct. I''ll also see if I can get the original demo libraries back online, not sure if I still have them somewhere.

The past year working actively with Omnis Studio 4 (at my previous work we were still doing most of our work in Studio 3) I have learned some new tricks and I''ve been writing actively on the omnis mailing list (http://www.omnis-dev.com/) about this. If I can find the time I may continue this series but I make no promises :)

Part 5...

Part 4...

Part 3....

And part two...

Part 1 of the tutorial I posted on www.omniscentral.com over a year ago. I''m still piecing things together so bare with me...