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Re: how to check if a property is empty?
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Re: how to check if a property is empty?


  • Subject: Re: how to check if a property is empty?
  • From: Quincey Morris <email@hidden>
  • Date: Sat, 29 Mar 2008 10:04:38 -0700


On Mar 29, 2008, at 08:32, Davide Benini wrote:

- (void) dealloc
{
	[repetitions release];
	[variantEnding release];

	[body release];
	[super dealloc];
}
- (id) init
{
	self = [super init];
	if (self != nil) {
		repetitions = [[NSNumber alloc] init];
		variantEnding = [[NSNumber alloc] init];
		body = [[NSMutableArray alloc] init];
	}
	return self;
}

I assign their value when it is needed.
Let's say I have an instance of this class, called *thisObject. How do I check whether I have assigned a value to thisObject.variantEnding or if the property is inialized but empty?

There's no intrinsic "initialized but empty" state of Objective C objects. 'variantEnding' can be initialized to nil (or, rather, allowed to remain nil, since everything in a new object is guaranteed to be zeroes) or it can be given a NSNumber value.


If you really *need* an 'empty' state, you can choose to regard nil as 'empty' if it suits your purposes -- that's often how it's done -- or you can choose use a specific value to mean 'empty' (e.g. [NSNumber numberWithInteger:NSNotFound] might be a possibility).

By the way, '[[NSNumber alloc] init]' is not likely to be a useful way to initialize a NSNumber instance variable. The NSNumber object *has* a value, even if you don't care what the value is at that point, so you may as well be explicit.


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