Skip to main content

Flex client-server data exchange

Flex programming is much like classic client-server stuff (at least, compared to a web app). So, here's a challenge we faced when designing viibee:

The user modifies data on the client and these mutations shall, of course, propagate to the server. The question is: shall the data be modified locally (on the client) before the server received the changes or shall the client modify the data only after the server has persisted the changes? Let's call these two scenarios "optimistic" and "pessimistic", respectively.

In the pessimistic model there is less chance of an inconsistency of the data between server and client. Also, the user can always be sure that his changes have really been persisted. But you loose a lot of responsiveness of the UI (and this is why you chose to do a RIA, isn't it?).

In the optimistic model you have a much more responsive UI. But you might need to implement certain logic twice, especially some data validation will have to be done on the client and maybe on the server again. Plus, you will have to handle the case that errors occur on the server.

We thought of the pessimistic model as a "banking app" and the optimistic model as "GMail". Interestingly enough, Adobe has described the optimistic model here and describe it in terms of a banking application.

In the end, we have chosen the optimistic model and have not looked back so far.

Comments

Popular posts from this blog

Python script to set genre in iTunes with Last.fm tags

Now that I have started to seriously use iTunes I figured it might be nice to have the genre tag set in a meaningful way. Since I have a reasonably large collection of mp3s doing that manually was out of question - I wrote me a Python script to do that. There seems to be a large demand for such a functionality (at least I found a lot of questions on how to automatically set the genre tag) so maybe someone else finds the script useful. It is pasted below.

General Strategy

The basic idea is to use Last.fm's tags for genre tagging. In iTunes the genre tag is IMO best used when it only contains one single genre, i.e. something like "Electronica", not something like "Electronica / Dance". On the other hand dropping all but one tag would lose a lot of information, so I decided to use the groupings tag for additional information that is contained in the list of tags that an artist has on Last.fm. In the example above that would be something like "Electronica, Dance…

mp3tagger on GitHub

On the mp3 tagger post I have received quite a bit of feedback and feature requests. Therefore, I thought it might be a good idea to do "social coding" and put the code on GitHub where it can easily be forked (and the forks can be watched).

Other than that, the latest version of the tagger contains these improvements:
the Last.fm keys and secret are not stored in the code anymore, but entered on the first run and stored in ~/.mp3tagger.cfgyou can run the script in two additional modes: simulation and ask. In simulation mode no changes to mp3s will be saved, in ask mode you will be asked to save each change. Start the script with flags "-m simulation" or "-m ask", respectively.It is now possible to specify a list of genre tags that will be considered (additionally to the mp3 default genre tags). The list needs to be stored in a config file at ~/.mp3tagger_genres.cfg (in the "generic" section of the file). The full format this file needs to have is …