javascript - 查找 Parse 数据库中最常出现的值

Question

我没有看到关于如何在 Parse 的表中找到最常出现的值的文档。我如何进行此查询(首选 iOS 答案，但不限于)

我想我可以使用某种带有 NSPredicate 的复合查询，但我仍然非常不确定如何进行此计算。

Answer 1

也许这对你有帮助:

NSArray *yourarray = [NSArray arrayWithObjects:@"X", @"Y", @"Z", nil];
NSCountedSet *yourset = [[NSCountedSet alloc] initWithArray:yourarray];

for (id item in yourset) {
    NSLog(@"Count of %@ is %lu", item, (unsigned long)[yourset countForObject:item]);
}

这可能是 NSPredicate 示例(没有尝试，因为我在 TextMate 中编写):

NSDictionary *dic1 = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:99] forKey:@"visitCount"];
NSDictionary *dic2 = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:2] forKey:@"visitCount"];
NSDictionary *dic3 = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1003] forKey:@"visitCount"];
NSDictionary *dic4 = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:1005] forKey:@"visitCount"];
NSDictionary *dic5 = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:107] forKey:@"visitCount"];
NSArray *array = [NSArray arrayWithObjects:dic1, dic2, dic3, dic4, dic5, nil];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF.visitCount == %@.@max.visitCount", array];

NSArray *result = [array filteredArrayUsingPredicate:predicate];
NSLog(@"Max in objects: %@", result);