[fpc-devel] Observer support in Delphi

[Graeme Geldenhuys]

On 25/10/12 00:55, luiz americo pereira camara wrote:
> - Initially i questioned the fpc obsever support, now i see as a good
> implementation

The FPC Observer and Mediator is based on works found in the tiOPF
framework - done a few years ago. And that in turn was based on a
implementation I done for our company back in 2005. The design and
functionality has a long history, is well tested in production software
- so yes, it is good. ;-)


> - ... (i would bet it was introduced to support the Live
> Bindings)

Yes I would imagine so. The tiOPF Observer & Mediator implementation is
the basis for our company's "live bindings", which we call
Model-GUI-Mediator (very similar to Model-View-Controller). This was
long before Delphi had Live Binding support. We have been using the
tiOPF implementation for 7 years in all our products, and all our
application's UI is Observer/Mediator driven. There isn't a single
DB-aware component in sight. I can hook up any gui control to a
data/business object property with a single line of code, and have 2-way
updates with no extra work.

Michael even took the tiOPF idea and built a non-tiOPF based design-time
support for Lazarus (this is where the current FPC Observer/Mediator
comes in) - though the design-time code was never contributed to the
Lazarus project. I'm sure he will at some point.


Anyway, to make a long story short. The current FPC Observer/Mediator is
a good design and very flexible with what it can offer. The Lazarus
project could very easily use this to implement their own "live
bindings" support. It could even make DB-aware components obsolete
(optional).


> (two implementations) since would
> have overlapping features with possible overhead (two observer lists per
> component?) at base classes

Yes indeed, having two implementations in FPC would definitely not be a
good idea!



   Graeme.