根据特定密钥重复NSArray NSArray

我试图根据词典中的特定键来删除NSArray的NSArray。我看到的是这样的：

NSDictionary *person1 = [NSDictionary dictionaryWithObjectsAndKeys:@"John", @"firstName", @"Smith", "lastName", @"7898", @"employeeID"];
NSDictionary *person2 = [NSDictionary dictionaryWithObjectsAndKeys:@"Eric", @"firstName", @"Johnson", "lastName", @"1718" @"employeeID"];
NSDictionary *person3 = [NSDictionary dictionaryWithObjectsAndKeys:@"John", @"firstName", @"Smith", "lastName", @"1153", @"employeeID"];

NSMutableArray *personArray = [NSArray arrayWithObjects:person1, person2, person3, nil];

// insert some code to de-dupe personArray based SOLELY on the firstName and lastName keys

请注意，有两名员工姓名相同但ID不同。我想做的只是回到一个只有person1和person2的新数组，因为person3具有相同的数据 - 我只是不关心这个特定问题中的“employeeID”值。有任何想法吗？谢谢！ -Matt