# Composition and inheritance: the Julian way

**URL:** <https://discourse.julialang.org/t/composition-and-inheritance-the-julian-way/11231>\
**Category:** General Usage\
**Tags:** inheritance, structtypes\
**Created:** [May 29, 2018, 1:06pm UTC](https://discourse.julialang.org/t/composition-and-inheritance-the-julian-way/11231 "2018-05-29T13:06:00Z")\
**Posts on this page:** 1\
**Showing post:** 39

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [June 1, 2018, 8:04am UTC](https://discourse.julialang.org/t/composition-and-inheritance-the-julian-way/11231/39 "2018-06-01T08:04:18Z")

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> [@Raf](#):
>
> This is a rule I’m going to take on from now on: methods in shared packages should _always_ dispatch on abstract types. Never on concrete types.
> 
> It really wasn’t entirely clear to me before this. It should be in the docs in bold all caps somewhere. Dispatching on concrete types is locking in implementation details and making lots of useless replication for anyone trying to extend types.

Yup, or even just let anything go.

> **[Type-Dispatch Design: Post Object-Oriented Programming for Julia - Stochastic...](http://www.stochasticlifestyle.com/type-dispatch-design-post-object-oriented-programming-julia/)**
>
> In this post I am going to try to explain in detail the type-dispatch design which is used in Julian software architectures. It’s modeled after the design of many different packages and Julia Base, and has been discussed in parts elsewhere. This is...

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