SwiftData: Batch delete failed due to mandatory OTO nullify inverse

Question

I'm trying to remove all data (for debugging purposes). Let's say I have two models:

@Model
class School {
    @Relationship(deleteRule: .nullify, inverse: \Student.school) var students: [Student]

    init(students: [Student]) {
        self.students = students
    }
}

and

@Model
class Student {
    var school: School?

    init() {}
}

I'm trying to delete everything like this:

try modelContext.delete(model: School.self)
try modelContext.delete(model: Student.self)

But I'm getting the error Batch delete failed due to mandatory OTO nullify inverse on Student/school. Why does it say "mandatory" when school is an optional value in Student?

Answer 1

To be able to use delete(model:) for a type with a relationship then both sides of the relationship needs to be optional.

So you need to change School

@Relationship(deleteRule: .nullify, inverse: \Student.school) 
var students: [Student]?

And if you don’t want to change your model then delete the objects one by one.

I assume this is a bug that nullify is ignored and that it will be fixed in the future.