Re: Why would a defined selector not be found at runtime?

Subject: Re: Why would a defined selector not be found at runtime?
From: Douglas Davidson <email@hidden>
Date: Thu, 12 May 2005 11:06:31 -0700

On May 12, 2005, at 10:53 AM, Ken Tozier wrote:

Allocating like this:

NSDisclosureButtonCell *result = [[NSDisclosureButtonCell alloc] initWithControlSize: inControlSize];

fails with the exact same error message as:

NSDisclosureButtonCell *result = [NSDisclosureButtonCell alloc];

// next line shows a valid object in "result"

NSLog(@"result = %@", result);

// chokes here

[result initWithControlSize: inControlSize];

error log:

*** -[NSDisclosureButtonCell initWithControlSize:]: selector not recognized

I've read in multiple places that you should never split it up like you're doing. It should always be alloc/init'd together.

Hadn't heard that. Although I never alloc/init in two steps unless there is a problem and I want to see what's happening...

The primary reason you should not alloc/init in two steps is that the init may return a different object. It can be done correctly--the correct code would be

NSDisclosureButtonCell *result = [NSDisclosureButtonCell alloc];

NSLog(@"result = %x", result);

result = [result initWithControlSize:inControlSize];

but the quoted code shows some of the obvious errors that make this a bad idea: (1) the return value of initWithControlSize: should replace result, but does not; (2) you cannot in general send any message other than an initializer to an alloc'd but uninitialized object, so you should not use %@ with result here.

Douglas Davidson

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Follow-Ups:
- Re: Why would a defined selector not be found at runtime?
  - From: Andy Lee <email@hidden>
- Re: Why would a defined selector not be found at runtime?
  - From: Ken Tozier <email@hidden>

References:
	>Why would a defined selector not be found at runtime? (From: Ken Tozier <email@hidden>)
	>Re: Why would a defined selector not be found at runtime? (From: Ricky Sharp <email@hidden>)
	>Re: Why would a defined selector not be found at runtime? (From: Ken Tozier <email@hidden>)
	>Re: Why would a defined selector not be found at runtime? (From: SA Dev <email@hidden>)
	>Re: Why would a defined selector not be found at runtime? (From: Ken Tozier <email@hidden>)

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