ios - How can I call aggregate functions for properties of relationships in Realm? -


is there way use aggregate functions properties in one-to-one , one-to-many relationship? here's simple example of structure i'm using:

class toy: object {     dynamic var purchasedate: nsdate?     dynamic var name: string = ""     let ratings = list<rating>()     dynamic var toyowner: person? }  class rating: object {     var stars: int = 0     var comments: string? }  class person: object {     dynamic var name: string = ""     dynamic var age: int = 0 }

i'd along lines of this:

// average age of owner of toys purchased within date range let avgage: double = realm.objects(toy)     .filter("purchasedate >= %@ && purchasedate <= %@", startdate, enddate)     .avg("person.age")  // sum stars given toys purchased within date range let totalstars: double = realm.objects(toy)     .filter("purchasedate >= %@ && purchasedate <= %@", startdate, enddate)     .sum("sum(ratings.stars)")

is there way these aggregate functions within realm?

although realm have aggregate value functions (see aggregate operations docs on realmcollectiontype), don't work multi-level keypaths person.age.

however, can of heavy lifting realm modifying queries:

// average age of owner of toys purchased within date range let ages = realm.objects(toy)     .filter("purchasedate between %@", [startdate, enddate])     .valueforkeypath("toyowner.age") as! [double] let avgage = ages.reduce(0, combine: +) / double(max(ages.count, 1))  // sum stars given toys purchased within date range let totalstars = realm.objects(toy)     .filter("purchasedate between %@", [startdate, enddate])     .reduce(0) { sum, toy in         return sum + toy.ratings.sum("stars") }

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