Relations

Object property type to indicate a to-one relation to another object.

Initialize with nil in your type declarations.

• You can set the value to nil to remove the relation. You can also set target or targetId to nil.
• You can set target to an object to set the relation. Call Box.put(_:) to persist the changes.
• You can set targetId to an object’s ID to set the relation. Call Box.put(_:) to persist the changes.

Example

class Person: Entity {
    var spouse: ToOne<Person> = nil
}

let personBox: Box<Person> = store.box(for: Person.self)
let amanda: Person = ...
let neil: Person = ...

amanda.spouse.target = neil
try personBox.put(amanda)

Remove a relation

amanda.spouse.target = nil
// ... or ...
amanda.spouse.targetId = nil
// ... are equivalent to:
amanda.spouse = nil
// ... whis is a short version of:
amanda.spouse = ToOne<Person>(target: nil)

Declaration of a to-many relationship to objects of a certain type.

Initialize with nil in your type declarations. The code generator will set different values.

Example:

class Customer: Entity {
    var id: EntityId<Customer> = 0

    /// Annotation with ReferencedType's property name is required; Order is "ReferencedType",
    /// Customer is "OwningType"
    // objectbox: backlink = "customer"
    var orders: ToMany<Order> = nil
    // ...
}

class Order: Entity {
    var id: EntityId<Order> = 0
    var customer: ToOne<Customer> = nil
    // ...
}

Removing relations

A ToMany can be modified just like any other RangeReplaceableCollection. Once you have changed your relation as needed, call applyToDb() on it to actually write the changes to disk.