I have a custom class I'm using instances of as keys in a dictionary. The problem is, sometimes
(not all the time) requesting a value from a dictionary with one of my custom
instance keys returns nil when the key really is in the dictionary. I looked
around the web on how to use custom objects as dictionary keys, and all I've
been able to find is that you need to implement the NSCopying protocol, which
I have done.
My class looks like this:
// .h
@interface MyObject: NSObject <NSCopying>
@property (copy) NSString* someString;
@property (copy) NSString* otherString;
@property int someInt;
+ (instancetype) objectWithString:(NSString*)str;
- (id) copyWithZone:(NSZone*)zone;
@end
// .m
@implementation MyObject
@synthesize someString;
@synthesize otherString;
@synthesize someInt;
+ (instancetype) objectWithString:(NSString*)str {
id obj = [[self alloc] init];
[obj setSomeString:str];
[obj setOtherString:[str lowercaseString];
[obj setSomeInt:0];
return obj;
}
- (id) copyWithZone:(NSZone*)zone {
id other = [[[self class] allocWithZone:zone] init];
[other setSomeString:self.someString];
[other setOtherString:self.otherString];
[other setSomeInt:self.someInt];
return other;
}
@end
Then I put some of these things in a mutable dictionary like this:
MyObject* key1 = [MyObject objectWithString:@"Foo"];
MyObject* key2 = [MyObject objectWithString:@"Bar"];
NSNumber* value1 = [NSNumber numberWithInt:123];
NSNumber* value2 = [NSNumber numberWithInt:456];
NSMutableDictionary* theDict = [[NSMutableDictionary alloc] init];
[theDict setObject:value1 forKey:key1];
[theDict setObject:value2 forKey:key2];
Now what I want to do is just pop a key/value pair out of the dictionary, so I do that like this:
MyObject* theKey = [[theDict allKeys] firstObject];
NSNumber* theValue = [theDict objectForKey:theKey];
And here's where I run into problems. Most of the time, this works fine.
However, sometimes objectForKey:theKey returns nil. I've put a breakpoint
in my code and can confirm that theKey is indeed in the theDict.
What am I doing wrong here?
