Aaron - you are almost there with the use of interfaces. Let's say that you have the following interfaces for your return results.
IHeightResult
IWeightResult
ILevelResult
If you specified the a return variable as:
var _something:*;
.and functions that return the result as:
public function getSomething():*
{.
.or used event handlers as:
public function somethingEventHandler( event:AnalyZOR, obj:* ):void
{.
You can always.
If ( obj is ILevelResult )
= > process as level result
Else if ( obj is IWeightResult )
= > process as weight result
Else if ( obj is IHeightResult )
= > process as height result
The trick is using the 'unspecified' type operator (asterisk) wherever you
are going to pass one of your three typed objects. One of the keys to
polymorphism is function overriding. which isn't available in AS 3.0 (you
probably found this out). So. one of the alternatives is to use the
'unspecified' identifier.
Rick Winscot
From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On
Behalf Of Aaron Miller
Sent: Sunday, March 23, 2008 2:51 AM
To: flexcoders@yahoogroups.com
Subject: Re: [flexcoders] Design pattern for conditional Interfaces ?
Hi Again, I'm not sure if this needs to be stated or not. But your switch
statement would look something like this.
# switch( true ) {
# case item is IHeightItem:
# //do stuff
# break;
# case item is ILevelItem:
# //do stuff
# break;
# default:
# //do stuff
# }
I was going to mention this but forgot to add it before I hit send.
Best Regards,
~Aaron
On Sat, Mar 22, 2008 at 11:43 PM, Aaron Miller
<[EMAIL PROTECTED]> wrote:
Polymorphisms is a run time technique. There is no way to determine a
dynamic class instance's interface at runtime. I would use a switch
statement in your AnalyzerBundle class to determine which interface an
analyzer implements and process accordingly, throwing an error on default if
necessary (realistically, you shouldn't have an unexpected interface). To
add new analyzer/interfaces, you would just have to add an item to the
switch statement and an appropriate method or class to handle it. Warning:
make sure to check extended interfaces in bottom up order.
I'm not sure if this is a generally excepted "design pattern", but it's what
I would do in this case.
Hope this helps,
~Aaron
On Sat, Mar 22, 2008 at 1:55 PM, Jeroen Beckers <[EMAIL PROTECTED]>
wrote:
Hi list!
Situation: I have a class that analyzes stuff. There are different analyzing
classes, suck as "HeightAnalyzer", "WeightAnalyzer", "LevelAnalyzer", etc.
You can add an analyzer to the class by using
'myClass.addAnalyzer(newAnalyzer:IAnalyzer)'. As you can see, there is an
IAnalyzer interface which all Analyzer's implement. Every time you add an
analyzer, it is added to the list using the Decorator pattern. (Every
analyzer must analyze a list and pass it to the next analyzing test)
Now, the analyzer's analyze certain items. Every analyzer requires a
different set of methodes. The HeightAnalyzer requires a getHeight(), the
LevelAnaylzer requires a getLevel(), etc. I want to have a different
interface for each analyzer, so that I can easily add analyzers
(+interfaces).
If I want to analyze a list of items, those items must implement the correct
interface, according to which analyzers you have added to the class. Fe:
var myClass:AnalyzerBundle = new AnalyzerBundle();
myClass.addAnalyzer(new HeightAnalyzer());
myClass.addAnalyzer(new LevelAnalyzer());
myClass.analyze(new Array(item1, item2, item3));
What I am looking for now, is a way to make sure that item1, item2 and item3
all implement the IHeightItem and ILevelItem interfaces.
I've found a couple of ways to do this, but none of them seemed really good
to me. One of them was to have every Analyzer keep track of the interface
associated with it, and check if they implement the correct interface, once
the analyzer is called. But this would give ugly runtime errors...
I'm pretty sure that it can't be done at compile time, but if anyone happens
to know some way (hack), or a better way for the runtime errors, please tell
me :-). All ideas are welcome
Ps: I've just made up all these names, my question is about the technique to
be used, not about the project :)
--
Aaron Miller
Chief Technology Officer
Open Base Interactive, LLC.
[EMAIL PROTECTED]
http://www.openbaseinteractive.com
--
Aaron Miller
Chief Technology Officer
Open Base Interactive, LLC.
[EMAIL PROTECTED]
http://www.openbaseinteractive.com
<<image001.jpg>>
<<image002.jpg>>
