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

Here is a Swift extension on the NSArray class that removes duplicates for the specified property:

extension NSArray {
/**
 - parameter property: the name of the property to check for duplicates

 - returns: an array of objects without objects that share an identical value of the specified property
*/
  func arrayWithoutObjectsOfDuplicateProperty(property : String) -> [AnyObject] {
    var seenInstances = NSMutableSet()

    let predicate = NSPredicate { (obj, bind) -> Bool in
      let seen = seenInstances.containsObject(obj.valueForKey(property)!)

      if !seen {
        seenInstances.addObject(obj.valueForKey(property)!)
      }
        return !seen
      }      
      return self.filteredArrayUsingPredicate(predicate)
  }
}