CODEWITHSUNDEEP
iosswiftcore-datapredicates
user1779394
user1779394

Reputation: 141

Count query Core Data predicate

i have a entity called schedule that has many alarms (other entity), i want to get only schedules that have less then 30 future alarms. Searching all around i get that query that not works /:

 let predicateFutureAlarms = NSPredicate(format: "(alarms.date > %@).@count < 30", NSDate().timeIntervalSince1970)

(on running time a (lldb) appears on console and appoints to the initialization of that variable)

Upvotes: 2

Views: 1228

Answers (1)

Martin R
Martin R

Reputation: 539775

There are at least two problems:

  • "(alarms.date > %@).@count < 30" is not a valid predicate syntax.
  • The %@ placeholder expects an object, but NSDate().timeIntervalSince1970 is a floating point number.

I cannot test it currently, but something like this should work:

let now = NSDate()
let predicate = NSPredicate(format: "SUBQUERY(alarms, $a, $a.date > %@).@count < 30", now)

For each Schedule object, the SUBQUERY(...) evaluates to all related alarms objects which have a date which is greater than now.

See "Predicate Format String Syntax" for a general description of the predicate syntax. The "SUBQUERY" expression is poorly documented, compare the NSExpression class reference or Quick Explanation of SUBQUERY in NSPredicate Expression.

Upvotes: 3

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