Re: multiple definitions of compare: -- design flaw?
Re: multiple definitions of compare: -- design flaw?
- Subject: Re: multiple definitions of compare: -- design flaw?
- From: James Quick <email@hidden>
- Date: Thu, 10 Jul 2003 15:13:37 -0400
On Thursday, July 10, 2003, at 01:21 PM, Brent Gulanowski wrote:
This is exactly my point: I AM writing another class that implements
compare -- only it's actually comparing items in a dictionary which
could be strings or numbers. I did not say that I wanted to compare
objects of different classes, only that I wanted to avoid the compiler
warning. Clearly one would want to ensure that one did not call
-compare: on NSString with anything but another NSString! But the same
program might want to compare two strings, two dates, two numbers or
two custom objects, without having an annoying compiler warning about
multiple declarations. Creating a warning when you aren't doing
anything wrong is ... or might be ... a bug.
The warning is useful alerting you to a possible runtime mismatch. It
is quite easy to quiet the warning.
Let's say your front end takes arguments as type id.
Your class determines the comparison argument arg1 must be sent to an
NSString comparison
method. When you pass arg1 to a method expecting a string you will
simply use a typecast
operation to declare the type. This would look like [aString compare:
(NSString *) arg1].
Obviously, you should not quiet the compiler with typecasts all the
time. Often they will
signal possible flaws in a design, or indicate a situation which might
cause a problem.
In your case, it appears to be a well thought out solution, and a
typecast is just what
you need to indicate to the compiler that you are aware you are passing
a parameter
which is appropriate, even though by context alone the compiler thought
it might
not be correct.
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