反向链接领域

Question

嗨，我正在玩 Realm，我正在尝试获取和输出：

Fido has 1 owners (["John"])
Rex has 2 owners (["Mary","Bob"])

虽然我不断得到这个输出：

Fido has 1 owners (["John"])
Rex has 1 owners (["Mary"])
Rex has 1 owners (["Bob"])

这是我正在使用的代码：

// this in the app delegate
 try! realm.write {
            realm.create(Person.self, value: ["John", [["Fido", 1]]])
            realm.create(Person.self, value: ["Mary", [["Rex", 2]]])
            realm.create(Person.self, value: ["Bob", [["Rex", 2]]])
        }

        // Log all dogs and their owners using the "owners" inverse relationship
        let allDogs = realm.objects(Dog)
        for dog in allDogs {
            let ownerNames = dog.owners.map { $0.name }
            print("\(dog.name) has \(ownerNames.count) owners (\(ownerNames))")
        }


class Dog: Object {
    dynamic var name = ""
    dynamic var age = 0
    var owners: [Person] {
        // Realm doesn't persist this property because it only has a getter defined
        // Define "owners" as the inverse relationship to Person.dogs
        return linkingObjects(Person.self, forProperty: "dogs")
    }
}

class Person: Object {
    dynamic var name = ""
    let dogs = List<Dog>()
}

如果你能提供帮助，谢谢。

Answer 1

从外观上看，您正在创建一个完全独立的 Rex 副本，每次您向数据库添加新所有者时，而不是重复使用同一个所有者。

最好提前单独创建Dog对象，然后在创建Person对象时直接引用这些对象。