# Changing struct fields to a different sub-type during run time

**URL:** <https://discourse.julialang.org/t/changing-struct-fields-to-a-different-sub-type-during-run-time/132346>\
**Category:** Modelling & Simulations\
**Tags:** question, performance, type, aerospace\
**Created:** [September 13, 2025, 12:56pm UTC](https://discourse.julialang.org/t/changing-struct-fields-to-a-different-sub-type-during-run-time/132346 "2025-09-13T12:56:01Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![Tortar](https://avatars.discourse-cdn.com/v4/letter/t/6bbea6/32.png) [@Tortar](https://discourse.julialang.org/u/Tortar)\
**Post date:** [September 14, 2025, 10:58am UTC](https://discourse.julialang.org/t/changing-struct-fields-to-a-different-sub-type-during-run-time/132346/7 "2025-09-14T10:58:20Z")

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Just to let you know, LightSimTypes.jl has been improved upon by WrappedUnions.jl, so I would suggest using that instead of it. See also the discourse announcement: [[ANN]: WrappedUnions.jl: Wrap a Union for enhanced type-stability](https://discourse.julialang.org/t/ann-wrappedunions-jl-wrap-a-union-for-enhanced-type-stability/132322)

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