从目标C中的数组获取唯一对象集的最佳方法是什么

Question

I have an array with list of model objects

model object has properties Name, Age, gender, I have date as follows

user* user1.name = "Bob", 
user1.age = "10",
user1.gender = "M",

user* user2.name = "Bob", 
user2.age = "11",
user2.gender = "M",

user* user3.name = "Woz", 
user3.age = "15",
user3.gender = "M",

user* user4.name = "Woz", 
user4.age = "16",
user4.gender = "M",

Now I need to get the unique name and lesser age as result.

user* user1.name = "Bob", 
user1.age = "10",
user1.gender = "M",

user* user3.name = "Woz", 
user3.age = "15",
user3.gender = "M",

what would be the efficient way to derive the above result. Thanks In advance Any Hint or help would appreciated.

Answer 1

You can simply iterate the array looking for the youngest users, storing each one in a dictionary keyed by name. Once you have iterated the array simply get all of the dictionary values as an array;

-(NSArray*)getYoungestUniqueUsersFromArray:(NSArray*)users {

    NSMutableDictionary* youngestUsersDict = [NSMutableDictionary new];

    for (User* user in users) {
        User* currentUser = youngestUsersDict[user.name];
        if (currentUser == nil || user.age < currentUser.age) {
            youngestUsersDict[user.name]=user;
        }
    }

    NSArray* youngestUsers = [youngestUsersDict allValues];

    return youngestUsers;
}

Answer 2

@interface User : NSObject
@property (nonatomic, strong) NSString *name;
@property (nonatomic, assign) int age;
@property (nonatomic, strong) NSString *gender;
@end

@implementation User
+ (instancetype)create:(NSString *)name gender:(NSString *)gender age:(int)age {
    User *user = [[User alloc] init];
    user.name = name;
    user.gender = gender;
    user.age = age;
    return user;
}

- (BOOL)isEqual:(id)object {
    if ([object isKindOfClass:[User class]]) {
        return [[(User *)object name] isEqualToString:self.name];
    }
    return NO;
}

- (NSUInteger)hash {
    return self.name.hash;
}
@end



- (void)viewDidLoad {
    [super viewDidLoad];

    NSArray *users = @[[User create:@"Bob" gender:@"M" age:11],
                       [User create:@"Bob" gender:@"M" age:9],
                       [User create:@"Bob" gender:@"M" age:10],
                       [User create:@"Woz" gender:@"M" age:25],
                       [User create:@"Woz" gender:@"F" age:36],
                       [User create:@"Woz" gender:@"F" age:23]];

    users = [users sortedArrayWithOptions:NSSortConcurrent usingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        User *a = obj1;
        User *b = obj2;

        NSComparisonResult nameResult = [a.name compare:b.name];

        if (nameResult == NSOrderedSame) {
            return a.age > b.age;
        }

        return nameResult;
    }];

    NSSet *unique = [NSSet setWithArray:users];

    for (User *user in unique) {
        NSLog(@"%@: %zd - %@", user.name, user.age, user.gender);
    }
}