# Chapter 6 - Error when performing manual migration

**URL:** <https://forums.kodeco.com/t/chapter-6-error-when-performing-manual-migration/107509>\
**Category:** Core Data by Tutorials\
**Created:** [April 30, 2020, 11:43pm UTC](https://forums.kodeco.com/t/chapter-6-error-when-performing-manual-migration/107509 "2020-04-30T23:43:22Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jvantoor](https://assets.chunter.kodeco.com/user_avatar/forums.kodeco.com/jvantoor/32/81494_2.png) [@jvantoor](https://forums.kodeco.com/u/jvantoor)\
**Post date:** [April 30, 2020, 11:43pm UTC](https://forums.kodeco.com/t/chapter-6-error-when-performing-manual-migration/107509/1 "2020-04-30T23:43:22Z")

</div>

This is my 3rd attempt to complete the manual migration as outlined in chapter 6. After being frustrated from error messages earlier this week, I decided to take a break and try it again in a few days.

Tonight I started chapter 6 from the beginning, making sure I followed every step and compared my work with the completed projects. All my code and settings appear to be correct, but I still get an error when launching the app:

Thread 1: Exception: “-[UnCloudNotes.Note attachments]: unrecognized selector sent to instance 0x600000b5c3c0”

![Screen Shot 2020-04-30 at 6.37.28 PM](https://files.chunter.kodeco.com/original/3X/7/2/72ee29cd90085b10811b9fb8d19ad924499e6058.png)

What did I do wrong? I included a copy of my project.

[UnCloudNotes.zip](https://forums.kodeco.com/uploads/short-url/qI97dP4MucPI0kPdx5fjlmhNgJO.zip) (125.8 KB)

EDIT: I noticed I didn’t set the note relationship as the inverse to the attachment relationship. I did change that, deleted and recreated the mapping mode, but now I get a different error:

Thread 1: Fatal error: Unresolved error Error Domain=NSCocoaErrorDomain Code=134140 “Persistent store migration failed, missing mapping model.” UserInfo={destinationModel=(\<NSManagedObjectModel: 0x60000268b5c0\>) isEditable 0, entities {

![Screen Shot 2020-04-30 at 7.49.15 PM](https://files.chunter.kodeco.com/original/3X/1/1/110f21f8d64c2f0e4f1f2432b709568b62880fca.png)

---

<div class="post-metadata">

**Author:** ![shogunkaramazov](https://assets.chunter.kodeco.com/user_avatar/forums.kodeco.com/shogunkaramazov/32/108826_2.png) [@shogunkaramazov](https://forums.kodeco.com/u/shogunkaramazov)\
**Post date:** [July 6, 2020, 12:21am UTC](https://forums.kodeco.com/t/chapter-6-error-when-performing-manual-migration/107509/2 "2020-07-06T00:21:22Z")

</div>

@jvantoor Please check out the update version of the book when you get a chance:

[https://store.raywenderlich.com/products/core-data-by-tutorials](https://store.raywenderlich.com/products/core-data-by-tutorials)

I hope it helps!

---

<div class="post-metadata">

**Author:** ![system](https://s3.amazonaws.com/cdn.raywenderlich.com/community/forum-assets/noun-game-ghost-878668.png) [@system](https://forums.kodeco.com/u/system)\
**Post date:** [October 14, 2020, 3:43pm UTC](https://forums.kodeco.com/t/chapter-6-error-when-performing-manual-migration/107509/3 "2020-10-14T15:43:24Z")

</div>

Closed on October 14, 2020, 3:43pm UTC

This topic was automatically closed after 166 days. New replies are no longer allowed.