Setting default values for inherited property without using accessor in Objective-C?
- by Ben Stock
I always see people debating whether or not to use a property's setter in the -init method. I don't know enough about the Objective-C language yet to have an opinion one way or the other. With that said, lately I've been sticking to ivars exclusively. It seems cleaner in a way. I don't know. I digress. Anyway, here's my problem … Say we have a class called Dude with an interface that looks like this:
@interface Dude : NSObject {
@private
NSUInteger _numberOfGirlfriends;
}
@property (nonatomic, assign) NSUInteger numberOfGirlfriends;
@end
And an implementation that looks like this:
@implementation Dude
- (instancetype)init
{
self = [super init];
if (self) {
_numberOfGirlfriends = 0;
}
}
@end
Now let's say I want to extend Dude. My subclass will be called Playa. And since a playa should have mad girlfriends, when Playa gets initialized, I don't want him to start with 0; I want him to have 10. Here's Playa.m:
@implementation Playa
- (instancetype)init
{
self = [super init];
if (self) {
// Attempting to set the ivar directly will result in the compiler saying,
// "Instance variable `_numberOfGirlfriends` is private."
// _numberOfGirlfriends = 10; <- Can't do this.
// Thus, the only way to set it is with the mutator:
self.numberOfGirlfriends = 10;
// Or: [self setNumberOfGirlfriends:10];
}
}
@end
So what's a Objective-C newcomer to do? Well, I mean, there's only one thing I can do, and that's set the property. Unless there's something I'm missing. Any ideas, suggestions, tips, or tricks?
Sidenote: The other thing that bugs me about setting the ivar directly — and what a lot of ivar-proponents say is a "plus" — is that there are no KVC notifications. A lot of times, I want the KVC magic to happen. 50% of my setters end in [self setNeedsDisplay:YES], so without the notification, my UI doesn't update unless I remember to manually add -setNeedsDisplay. That's a bad example, but the point stands. I utilize KVC all over the place, so without notifications, things can act wonky.
Anyway, any info is much appreciated. Thanks!
