On 10/26/05, Hal Helms <[EMAIL PROTECTED]> wrote:
> Why not just have an isNull(propertyName) method rather than litter classes
> with hasSpouse, hasX, has Y?
Yuck. Yuck. Yuck.
The idea that you get a spouse from a person and then do something
with the spouse already violates the Law of Demeter. If you have to
check if the person has a spouse before calling getSpouse() you're
probably asking the client code to do something that should be
encapsulated in person itself.
Instead of this:
<cfif person.hasSpouse()>
<cfset spouse = person.getSpouse()/>
<cfset spouse.foo()/>
</cfif>
You should work toward something like this:
<cfset person.fooSpouse()/>
<!--- in person.cfc --->
<cffunction name="fooSpouse">
<cfif structKeyExists(variables, "spouse")>
<cfset variables.spouse.foo()>
</cfif>
</cffunction>
Now the client code doesn't have to worry about using person
incorrectly (i.e. calling hasSpouse() on a person who is not married).
It doesn't have check preconditions or handle exceptions.
Back to Hal's question.
> Why not just have an isNull(propertyName) method rather than litter classes
> with hasSpouse, hasX, has Y?
Because if your class is littered wih hasSpouse, hasX, hasY methods,
your class is likely has a problem. An isNull(propertName) covers over
the problem, just as set(propertyName) and get(propertyName) methods
cover over the problem of public fields.
Although I suspect Hal knows that and he's just checking to see who's
been paying attention. :)
Patrick
--
Patrick McElhaney
704.560.9117
http://pmcelhaney.weblogs.us
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