Remove duplicates from array comparing the properties of its objects

Question

Suppose I have a class Event, and it has 2 properties: action (NSString) and date (NSDate).

And suppose I have an array of Event objects. The problem is that \"date\" pr

Answer 1

You can create an NSMutableSet of dates, iterate your event list, and add only events the date for which you have not encountered before.

NSMutableSet *seenDates = [NSMutableSet set];
NSPredicate *dupDatesPred = [NSPredicate predicateWithBlock: ^BOOL(id obj, NSDictionary *bind) {
    Event *e = (Event*)obj;
    BOOL seen = [seenDates containsObject:e.date];
    if (!seen) {
        [seenDates addObject:e.date];
    }
    return !seen;
}];
NSArray *events = ... // This is your array which needs to be filtered
NSArray *filtered = [events filteredArrayUsingPredicate:dupDatesPred];