[Seaside] [how to?] sesssion expiration
avi at beta4.com
Tue Jan 20 20:42:35 CET 2004
On Jan 20, 2004, at 8:35 AM, Vaidas Didzbalis wrote:
> I do not understang usage of isolate: ...
> How to modify Counter example, if I want user not be able press back
> and submit if value of counder is greater then 10?
Well, you can't quite use #isolate: for that, but you can use the
underlying WATransaction mechanism. First let me give an example of
what that would look like, then I'll try to explain:
WAComponent subclass: #WACounter
instanceVariableNames: 'count txn'
self session registerObjectForBacktracking: self.
count _ 0.
txn _ WATransaction new.
self session addFilter: txn
count _ count + 1.
count > 10 ifTrue: [self session removeFilter: txn. txn
What does this do? Well, the session keeps a stack of "filters" that
you can add to or remove from. Whenever a new page is generated, part
of the information that is recorded about it is what the active filter
objects are. When someone tries to use that page, their request first
passes through whichever filters were active. In this case, we are
putting an instance of WATransaction on the filter stack for the period
between the counter being created and the counter reaching 10. That
means that any interactions with any pages generated in that time will
have to pass through the WATransaction.
What WATransaction does is very simple. At first, it lets all requests
through, and they get processed normally. However, once you send it
#close, it will refuse any requests using WASession>>pageExpired.
Since we close the txn once we hit 10, then any attempts to use the
pages generated before we hit 10 will fail.
#isolate: is just a convenience wrapper around this - if you look at
its implementation you'll find it straightforward.
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