On Sunday 15 July 2001 21:45, you wrote:
Subject: The Adapter pattern inplemented with filters(code from distribution)
The code below from the XOTcl distribution is given below. Suppose the class Adapter has another filter "filter2" registered after the filter "adapterFilter". My understanding of the code(below) is that only requests that are not found in specificRequest will be filtered by filter2.
yes ... that is correct for the Adapter implementation below. Usually you would prepend filter2 before adapterFilter (with filter "filter2 [[self] info filter]") in order to ensure that filter2 is called before adapterFilter.
However, if this does not work for you, you can also refine the Adapter implementation to your requirements. Say, by calling next before adapting to the adaptee ...
--uwe
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Question: If my understanding is correct, how can I have all messages/requests to Adapter be filtered by both filters. ..........................................................
Code from distribution:
Class Adapter -superclass Class
Adapter metadata add description
Adapter metadata description { Simple adapter pattern meta-class taken from the paper 'Filters as a Language Support for Design Patterns in Object-Oriented Scripting Languages'. }
Adapter instproc adapterFilter args { # Appears that filter args == args of triggering method set r [self calledproc] [self] instvar specificRequest adaptee #puts [self] if {[info exists specificRequest($r)]} { #puts $args return [eval $adaptee $specificRequest($r) $args] } next }
Adapter instproc init args { [self] filterappend [self class]::adapterFilter next [self] instproc setRequest {r sr} { [self] set specificRequest($r) $sr } [self] instproc setAdaptee {a} { [self] set adaptee $a } }
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