Hi all,

It has been some time since I have used FPC/Laz. I was looking for some information on 'observer pattern' the other day, and I found this article[1]. I notice that it is a bit old, and it makes me question whether or not I have made an error following it.

I get an invalid cast error at this code
   (DigitalClock1 as ISubject).Attach(fClockTimer as IObserver);
which is actually flipped and should be
   (fClockTimer as ISubject).Attach(DigitalClock1 as IObserver);

So, my questions ...
Is the article out of date?
Are these patterns implemented in the base code?
And as an aside, what is the state of tiOPF, I could not get it to install in Lazarus 1.02.

Thank you.

[1] - http://blogs.teamb.com/joannacarter/2004/06/30/690

While stepping through the code I found that I had made an error.

I am still interested in the other questions.

Thank you.

You might find some info on the list archive for fpc-devel: http://lists.freepascal.org/lists/fpc-devel/2012-October/030149.html

bsquared wrote

And as an aside, what is the state of tiOPF, I could not get it to install in Lazarus 1.02.

tiOPF2 works with Lazarus but the visual data-components included in tiOPF do not work.
It is not a big problem because you can still use the persistence system and MGM (Model GUI Mediator).

Juha

The observer pattern is implemented in tiOPF.

And as an aside, what is the state of tiOPF, I could not get it to install in Lazarus 1.02.

Version 3 is designed to work with Delphi 2009 and higher. Graeme Geldenhuys actively maintains tiOPF version 2. It works definitely with Lazars 1.0.2, I use it myself.

Michael.

Thank you for responding.

What version of tiOPF should I use. I tried both 2 and 3, but got several different errors when attempting to compile demos.

Thank you for responding. I thought I recalled a stipulation for version 3. I noticed it had an Compilers/FPC folder, so I hoped it was compatible.

Having trouble getting V2 demos to work. Have to
Regards,
Brian

bsquared wrote

Having trouble getting V2 demos to work. Have to is a different folder for Lazarus demos. The AddressBook demo is

the most comprehensive. I don't have it installed on this machine so cannot check the paths.

Juha

Correct. I gave up trying to implement the tiOPF-aware GUI components with LCL, because LCL and the Lazaurus Forms Designer was simply too buggy. Others are welcome to contribute to this.

MGM is just another implementation of Model-View-Controller with a few tweaks to work better with more modern GUI toolkits that have there own events built-in.

MGM has been used in production systems since 2006, so works very well, and supports fpGUI, LCL and VCL. Any standard GUI components not supported by MGM yet, can very easily (a matter of minutes) be supported.

To getter a better background on MGM and how it uses the Observer and Mediator design patters, you can look at an old article I wrote for the Toolbox magazine.

http://opensoft.homeip.net/articles/

There are a few other articles up there too.

What version of tiOPF should I use. I tried both 2 and 3, but got several different errors when attempting to compile demos.

For use with FPC - you can only use tiOPF2. tiOPF3 is currently Delphi only because it only supports Delphi 2009 and newer features. FPC is still too incompatible to those Delphi versions.

Regards,
- Graeme -

bsquared wrote

> Graeme Geldenhuys actively maintains tiOPF version 2.

Yeah, his always hard at work. ;-)

> It works > definitely with Lazars 1.0.2, I use it myself.

+1

Thank you for responding. I thought I recalled a stipulation for version 3. I noticed it had an Compilers/FPC folder, so I hoped it was compatible.

tiOPF3 was forked from tiOPF2 a few years back, so the directory structures are identical. We left the Compilers/FPC directory in tiOPF3, but not expecting FPC to take so long to catch up to Delphi languages features.

Having trouble getting V2 demos to work. Have to demos have you tried? I'm reworking and reorganizing the Demos

directory as we speak. You should try the Demos/LCL/ directory if you use LCL toolkit, or Demos/fpGUI/ if you use the fpGUI toolkit. I haven't ported all the VCL demos to LCL or fpGUI yet, but the code is near identical. So even though you can't run the VCL demos, you can still look at them and learn from the code. If still lost, pop in at tiopf.support newsgroup and I'll help where I can.

Using a NNTP news client like Thunderbird:
news://news.tiopf.com

Or using a web browser via the web interface:
http://opensoft.homeip.net/webnews/

Regards,
- Graeme -

Thank you. I'll check in at tiopf for follow up.