Re: Question about + & -
Re: Question about + & -
- Subject: Re: Question about + & -
- From: Gregory Weston <email@hidden>
- Date: Thu, 13 Nov 2003 20:04:45 -0500
On Nov 13, 2003, at 16:00, Daniele wrote:
hello, I have a class with one connected NSTextField. A method inside
this class should permits to change the value of this field. Now I need
to call this method from different classes of my project, so I have
changed the method from - to + but unfortunatly there is a problem: i
cannot access to my NSTextField from the class method. Why? Can I solve
this problem without using the PostNotification method?
Because your connection is stored in an instance variable, and a class
method doesn't receive a reference to an instance of that class so
there's no instance variable to interact with. I think you may have
misunderstood the implication of - and +. Class methods (+) are methods
that operate on or on behalf of the class as a concept. Instance
methods (-) operate on a specific instance of a class. They really
don't have anything to do with whether the method can be invoked from
elsewhere.
You've got two basic options. Change it back to an instance method, and
make sure anything that wants to send the message knows about the
instance, or leave it as a class method and let the class manage a
singleton or default instance that it will manipulate when that message
is received.
G
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