将日期与空值比较

Question

I am showing some posts (created by the users) in an activity using a custom adapter. In the constructor of the custom adapter, I am using the following code to get the query result.

ParseQuery query = new ParseQuery("Post");
query.whereWithinMiles("location_point", my_point, 500);
query.whereGreaterThan("expire_date", new Date());
return query;

The target is - the user can set an expire date with each post so that the post will no longer be visible after the expiration. I am trying to compare the expire_date column with current time for checking if the post is expired or not.

The line query.whereGreaterThan("expire_date", new Date()); was added later. All the previously created rows has a null value in the expire_date column.

So each time I run the query, all the rows that has a date object in expire_date column are being checked according to the condition. The rows having a null value in expire_date column are never returned .

Note: The expire_date column is not a mandatory field (user can choose to leave it empty during creating a post).

Yes, I can set a default date for all the empty/null fields to compare with the expire date. But I was curious to know if there is a way so that I can either return all the rows having a null value or compare the current time with a null object with the whereGreaterThan condition?

Answer 1

ParseQuery notExpiredPosts = new ParseQuery("Post");
query.whereGreaterThan("expire_date", new Date());

ParseQuery noExpiredDate = new ParseQuery("Post");
query.doesNotExist("expire_date");

ParseQuery expiredDateQuery = ParseQuery.or(notExpiredPosts, noExpiredDate);

ParseQuery query = new ParseQuery("Post");
query.whereWithinMiles("location_point", my_point, 500);
query.whereMatchesKeyInQuery("objectId", "objectId", expiredDateQuery);
return query;

[(NotExpiredPost || NoExpiredDate) & (location_point within 500 mile)]

This is what you want, isn't it?

Hope this helps :)