[Gambas-user] constructor events

[B Bruen]

On Wed, 25 Jun 2014 09:15:01 +0200
Fabien Bodard <gambas.fr at ...626...> wrote:

> I really dont understand in what case it can be usefull
> 
> Your observer in all case will be created after the object so in this case
> just call a subroutine will do the same
> 
> If you need an info during the init you can give it as param
> 
> Please give more explanation of what you want to achieve
> 
> Regards
> 
> Fabien

It's to do with a class that handles a continuous XML feed for a set of similar feeds.  So we have a main form class that creates up to 15 or so instances of a "feed watcher" class, each looking at one specific thread.  We have certain handlers in the main class that respond to events raised in the feed-watcher class.  Once the feed-watcher object is fully instantiated these event handlers work fine and the set of feeds is managed fine.  However, some of these events can occur during the feed-watcher constructor execution.  Since we already have the code to handle them in the main form, I was hoping to not have to create special error conditions etc sent back from the feed-watcher._new method, but just to raise the relevant during the constructor.

The feeds are from a url like "www.xyz.com/auctions/lots.aspx?year=2014&month=6&day=26&lot=113#1".  Where 113 is one of a set of lot numbers we are interested in.  These feed-watchers set up the download structure, get the initial xml result and parse it (read on), then wake up on a timer basis and re-request the same url, get the result (its an XML document), parse it and depending on some changes to the parsed information, raise events that signal to the main form that something has to be done, for example, the bidding on that lot has started, finished, etc .  As it's an internet based feed, there are some other things that can also happen that we need to handle - download errors, loss of connection etc. Further, depending on the auction house concerned, setting up the download structure and getting the initial packet is complex. So we have a set of these feed-watcher classes specialised to handle that initial work.
 
The problem is that some of the conditions that result in the raising of these events can also happen during the construction of the feed-watcher object, e.g. loss of connection, but also some of the information based events, e.g the requested lot has been "cancelled" etc.

As I said, once the feed is established,everything works fine.  It's just that initial phase.

The more I think about it, the more I am convinced that it cannot work the way we have designed and written it. And we will have to split the initial phase into a constructor and an "Initialise" method. So never mind.

(Well, you did ask :-) )

regards
Bruce 


-- 
B Bruen <bbruen at ...2308...>