Member type

[whatyouhide]

A pretty common possible option value is a member of a list. An example that comes to mind is Broadway's :batch_mode in Broadway.test_messages/3, which is :bulk or :flush.

Do we want to support a "member" type?

schema = [
  batch_mode: [type: {:member, [:bulk, :flush]}, default: :flush]
]

Do you think it's too soon, too specific, or a good addition?

[josevalim]

Sounds good to me but I think :one_of would be a better name?

[whatyouhide]

@josevalim I wanted to keep one_of for the possibility of compound types later on (such as {:one_of, [:integer, :string, :atom]}. Thoughts?

[josevalim]

@whatyouhide I would say that is a :union. :)

[whatyouhide]

@josevalim fair enough, I'll make a PR for :one_of then.

[wojtekmach]

I like this proposal. Should this support a list or more generally any enumerable?

Btw, when I was evaluating libraries like Saul and Norm I arrived at the following list of operations that seemed useful

• all_of([a, b, ...]) - a and b and ... - intersection
• any_of([a, b, ...]) - a or b or ... - union
• one_of([a, b, ...]) - a xor b xor ... - symmetric difference (also known as disjunctive union)

:symmetric_difference doesn't quite has the same ring to it as the other two but it is by far less common :)

[josevalim]

In our case, since we don’t generate, I think only one_of is possible?

[whatyouhide]

This brings up the reason why I wanted to call it :member. Membership is about: is this value in this list (or set potentially)? The elements of the list are simple elements, not other validators. It's easy to implement and use. Thoughts?

[josevalim]

I would use one_of for values and union/intersection for types. Member sounds weird for some reason. ::