Is it possible to reset SwiftData to a state identical to that of a newly installed app?
I have experienced some migration issues where, when I add a new model, I need to reinstall the entire application for the ModelContainer creation to work.
Deleting all existing models does not seem to make any difference.
A potential solution I currently have, which appears to work but feels quite hacky, is as follows:
let _ = try! ModelContainer()
modelContainer = try! ModelContainer(for: Student.self, ...)
This seems to force out this error CoreData: error: Error: Persistent History (66) has to be truncated due to the following entities being removed: (...) which seems to reset SwiftData.
Any other suggestions?
Post
Replies
Boosts
Views
Activity
Are SwiftData queries lazy loaded when used in conjunction with SwiftUI List?
@Query
var posts: [PostModel]
List {
ForEach(posts, id: \.id) { post in
PostView(post)
}
}
If the code above is not lazy loaded, how can we make it lazy loaded?
With Core Data and SwiftUI we can use @SectionedFetchRequest. Does SwiftData support something similar to @SectionedFetchRequest?
For example, I want to create a lazy-loaded list that groups posts by their date.
@Model Post {
let title: String
let dateString: String // YYYY-MM-DD
let createdAt: Date
}
@SectionedFetchRequest(
entity: \Post.self,
sectionIdentifier: \Post.dateString,
sortDescriptors: [\Post.createdAt]
)
var postsByDate: SectionedFetchResults
ForEach(postsByDate) { section in
Section(header: Text(section.id)) {
ForEach(section) { post in
PostView(post)
}
}
}
Doing a batch delete on a many-to-one relationship seems to throw this error
CoreData: error: Unhandled opt lock error from executeBatchDeleteRequest Constraint trigger violation: Batch delete failed due to mandatory OTO nullify inverse on Student/school and userInfo {
NSExceptionOmitCallstacks = 1;
NSLocalizedFailureReason = "Constraint trigger violation: Batch delete failed due to mandatory OTO nullify inverse on Student/school";
"_NSCoreDataOptimisticLockingFailureConflictsKey" = (
);
}
If I try to delete the School in the one-to-many relationship, both the school and the students are deleted as expected.
However, If I try to delete all students the error is thrown. I would expect all students to be removed, while keeping the School intact.
Do SwiftData support this?
import XCTest
import SwiftData
@Model
class School {
var name: String
@Relationship(deleteRule: .cascade, inverse: \Student.school)
var students: [Student] = []
init(name: String) {
self.name = name
}
}
@Model
class Student {
var name: String
var school: School?
init(name: String) {
self.name = name
}
}
final class Test: XCTestCase {
func testScenario() throws {
let config = ModelConfiguration(isStoredInMemoryOnly: true)
let modelContainer = try ModelContainer(for:
School.self,
Student.self,
configurations: config
)
let context = ModelContext(modelContainer)
context.autosaveEnabled = false
let school = School(name: "school")
context.insert(school)
let student1 = Student(name: "1")
let student2 = Student(name: "2")
context.insert(student1)
context.insert(student2)
student1.school = school
student2.school = school
XCTAssertEqual(school.students.count, 2)
XCTAssertEqual(student1.school?.id, school.id)
XCTAssertEqual(student2.school?.id, school.id)
try context.save()
let newContext = ModelContext(modelContainer)
// try newContext.delete(model: School.self) // This works
try newContext.delete(model: Student.self) // This one fails
}
}
Given the code below the students array on the school is not being updated. Why?
Since the relationship is explicit and non-optional I would expect this to work.
import XCTest
import SwiftData
@Model
class School {
var name: String
@Relationship(deleteRule: .cascade, inverse: \Student.school)
var students: [Student]
init(name: String, students: [Student]) {
self.name = name
self.students = students
}
}
@Model
class Student {
var name: String
var school: School
init(name: String, school: School) {
self.name = name
self.school = school
}
}
final class Test: XCTestCase {
func testScenario() throws {
let modelContainer = try ModelContainer(for:
School.self,
Student.self
)
let context = ModelContext(modelContainer)
context.autosaveEnabled = false
let school = School(name: "school", students: [])
context.insert(school)
let student1 = Student(name: "1", school: school)
let student2 = Student(name: "2", school: school)
context.insert(student1)
context.insert(student2)
XCTAssertEqual(school.students.count, 2) // XCTAssertEqual failed: ("0") is not equal to ("2")
}
}