NSArray: Remove objects with duplicate properties

Question

I have an NSMutableArray that contains a few custom objects. Two of the objects have the same properties such as title and author. I want to remove the duplicate object an

Answer 1

You can use the uniqueness of an NSSet to get distinct items from your original array. If you have the source code for Assest you will need to override the hash and isEqual: method on the Asset class.

@interface Asset : NSObject
@property(copy) NSString *title, *author;
@end

@implementation Asset
@synthesize title, author;

-(NSUInteger)hash
{
    NSUInteger prime = 31;
    NSUInteger result = 1;

    result = prime * result + [self.title hash];
    result = prime * result + [self.author hash];

    return result;
}

-(BOOL)isEqual:(id)object
{
    return [self.title isEqualToString:[object title]] && 
    [self.author isEqualToString:[object author]];
}

- (void)dealloc {
    [title release];
    [author release];
    [super dealloc];
}

@end

Then to implement:

Asset *asset;
NSMutableArray *items = [[[NSMutableArray alloc] init] autorelease];

// First
asset = [[Asset alloc] init];
asset.title = @"Developer";
asset.author = @"John Smith";
[items addObject:asset];
[asset release];

// Second
asset = [[Asset alloc] init];
asset.title = @"Writer";
asset.author = @"Steve Johnson";
[items addObject:asset];
[asset release];

// Third
asset = [[Asset alloc] init];
asset.title = @"Developer";
asset.author = @"John Smith";
[items addObject:asset];
[asset release];

NSLog(@"Items: %@", items);

NSSet *distinctItems = [NSSet setWithArray:items];

NSLog(@"Distinct: %@", distinctItems);

And if you need an array at the end you can just call [distinctItems allObjects]