Most frequent occurrence of Realm
Realm Results
implement RealmCollectionType
RealmCollectionType
has property count
and aggregate operations max(_:)
.
What you need to do is something like (the following pseudocode won't compile if you just specify a dot):
results.filter {element in element.count == results.max (byCount)}. first
Any operation on an object Result
is performed in Realm database
, not in the device's memory.
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You can get all the objects Person
associated with your column supervisor
(a List<T>
?) And count name
between those objects Person
, where the natural maximum follows.
var frequencies = [String: Int]()
for person in yourRealmObject.supervisor {
frequencies[person.name] = (frequencies[person.name] ?? 0) + 1
}
if let mostCommonName = frequencies.max(by: { $0.value < $1.value })?.key {
// ... mostCommonName holds string "John" (if that is most common)
}
Naturally, more than one name may be the most common in your column, in which case you may need to return an array from the most common
if let mostCommonNames = frequencies.values.max()
.map({ maxCount in frequencies.filter { $0.value == maxCount }.map { $0.key } }) {
// ... mostCommonNames [String]
}
Or, if you really want to count the occurrences of the same object (instead of looking at a property name
: for example, there may be several different Person
: s s name
"John"
), you might consider making your object Person
match Hashable
and count the frequencies of real unique objects ( rather than frequencies of different values of name
object properties ).
// Person is Hashable ...
frequencies = [Person: Int]()
for person in yourRealmObject.supervisor {
frequencies[person] = (frequencies[person] ?? 0) + 1
}
// ...
Since it Person
is a reference type, the key
one corresponding to the most common object will be a reference to that object (for example "John"
Person
).
However, I may not follow your question: please expand it if this is not what you need.
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You have Person
and want to get one of your Person
supervisors objects matching the given name:
class Person: Object {
dynamic var name: String = String()
let supervisors = List<Person>()
convenience init(name: String) {
self.init()
self.name = name
}
}
let realm = try! Realm()
var me: Person!
try! realm.write {
me = Person(name: "Me")
for supervisor in ["John", "Mary", "Phil"] {
me.supervisors.append(Person(name: supervisor))
}
realm.add(me)
}
let john = me.supervisors.filter("name == 'John'")[0]
print(john)
Prints:
Person {
name = John;
supervisors = RLMArray <0x6080000f2280> (
);
}
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