Question

我没有看到如何在Parse中查找表中最常出现的值的文档。如何进行此查询（iOS回答首选，但不限于此）

我认为我可以使用NSPredicate进行某种复合查询，但我仍然不确定如何进行此计算。

Answer 1

也许这可以帮助你：

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的例子（没试过，因为我在TextMate中写道）：

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);

在Parse数据库中查找最常出现的值

1 个答案: