# How do you actually find out \*how\* to use an interface in Julia, like the concept of iterator "end"?

**URL:** <https://discourse.julialang.org/t/how-do-you-actually-find-out-how-to-use-an-interface-in-julia-like-the-concept-of-iterator-end/134796>\
**Category:** New to Julia\
**Created:** [December 29, 2025, 7:09pm UTC](https://discourse.julialang.org/t/how-do-you-actually-find-out-how-to-use-an-interface-in-julia-like-the-concept-of-iterator-end/134796 "2025-12-29T19:09:39Z")\
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**Author:** ![raman\_kumar](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raman_kumar/32/26782_2.png) [@raman\_kumar](https://discourse.julialang.org/u/raman_kumar)\
**Post date:** [December 29, 2025, 7:43pm UTC](https://discourse.julialang.org/t/how-do-you-actually-find-out-how-to-use-an-interface-in-julia-like-the-concept-of-iterator-end/134796/2 "2025-12-29T19:43:09Z")

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If you would have defined the iteration condition like `for i in 1:10` then `i==10` will be the iteration end condition.

> **[Iteration - Interfaces · The Julia Language](https://docs.julialang.org/en/v1/manual/interfaces/#man-interface-iteration)**
>
> A lot of the power and extensibility in Julia comes from a collection of informal interfaces. By extending a few specific methods to work for a custom type, objects of that type not only receive those functionalities, but they are also able to be...

See that `iterate(iter, state) == nothing` is the condition for iteration end.  
May be this post can be of help [Understanding iterate() documentation is tough](https://discourse.julialang.org/t/understanding-iterate-documentation-is-tough/134715).

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