That sort of make sense. (But the calling code has to know the object is no
longer reporting gallons also... isn't that a violation of the encapsulation
concept?)

The second example has merit... since age is always relative to the time
checked. So unless you could have a variable that reported like a method
there would be an issue.

Thanks....
John

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Barney Boisvert
Sent: Monday, August 29, 2005 4:19 PM
To: [email protected]
Subject: Re: [CFCDev] When to use the THIS scope for a ColdFusion Component?

What if the units in the DB change from gallons to litres? You don't
want getGasLeft so start returning a value 3.8 times larger than
expected.  So you'd deprecate that method, and then add
getGasLeftGallons() and getGasLeftLitres() or something.  You don't
get that protection with instance variables, because as soon as the
switch happens, the instance variable's semantics change, and with no
indication.

Another example is getAge(), because you very likely aren't storing an
'age' variable, but rather than 'dateOfBirth' variable that needs
computation.  But the calling code shouldn't care (or even be able to
tell); that's encapsulation.

Autogenerated get/set methods aren't any more helpful than just
exposing the raw data members.  The encapsulation only comes when
they're actually encapsulating something, usually a conversion from
the publicly exposed properties to the actual internal representation.

cheers,
barneyb



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