How to handle a focus that isn't in the structure? about lens HOT 8 CLOSED

Lens.satisfy(&(&1)) is what i used
this may be worthy of adding to the library as an idiom
or do you know of a different way to do this that is better/idiomatic?

from lens.

Not quite sure what you mean - could you post an example?

from lens.

Do you mean you want something like:

iex> Lens.to_list(lens, %{a: 1})
[1]
iex> Lens.to_list(lens, %{})
[]

from lens.

yeah, so i had a parent node that is sometimes nil, and i focus on it's children.
so similar to what you posted

from lens.

example
:secondary is sometime nil

    people_lens =
      Lens.multiple([
        Lens.key(:primary),
        Lens.key(:secondary)])
      |> Lens.satisfy(exists) #existence check

    age_lens =
      people_lens
      |> Lens.both(Lens.key(:children) |> Lens.all)
      |> Lens.key(:age)

from lens.

Yeah, I think Lens.satisfy(&(&1)) is fine for this case... Not sure if there should be a separate function for this if such an easy solution exists.

from lens.

I think it may not be obvious.
may need more examples of how to use the library.

from lens.

If you think you have a way to make this obvious in the API, please make a PR, closing for now.

from lens.