# Error in migration from v3 to v4 (Custom migration Policy)

**URL:** <https://forums.kodeco.com/t/error-in-migration-from-v3-to-v4-custom-migration-policy/110425>\
**Category:** Core Data by Tutorials\
**Created:** [May 28, 2020, 12:16pm UTC](https://forums.kodeco.com/t/error-in-migration-from-v3-to-v4-custom-migration-policy/110425 "2020-05-28T12:16:45Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**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 7, 2020, 12:46am UTC](https://forums.kodeco.com/t/error-in-migration-from-v3-to-v4-custom-migration-policy/110425/2 "2020-07-07T00:46:39Z")

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@alokc83 Please check out the updated version of the book:

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

I hope it helps!

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