starting to try to replace my Virtus addiction by dry-types 😜
I have a domain object that maps a remote API resource object ... and for example some of the attributes are DateTime instances
& for example, the responsability of coercion for DateTime values should be done outside of the object itself?
it won't coerce anything and will just put a string on the object state
User.new(schema.call(some_data_from_api)) <= just this
of course validation can fail so you may want to handle this however you want
but that forces the schema to be defined twice somehow, right?
on the struct, and on the schema definition
and the schema definition contains validation logic, also
and how will a DateTime coercion/parsing will be done on a Schema object :/
I’d do something like this:
UserSchema = Dry::Validation.JSON do
required(:created_at).value(:date_time?)
end
class User < Dry::Struct
attribute :created_at, Types::Strict::DateTime
end
user_attrs = UserSchema.(user_data)
User.new(user_attrs)
in 1.0.0 dry-validation will support infering schemas from struct definitions, for now you need to have it defined explicitly in both places
this is the service object where I'm trying to inject that Schema logic you're talking about
so that you understand the context a little better
anyhow, yes it will enforce coercions
let's say ... users that never logged in, the last_sign_in_at datetime doesn't exist
don't even know if I just tell the API owners to returning an empty field or just skip the field on the response
so, uhm, you can do all sorts of things to make it easier to work with potentially garbage-data
unfortunately JSON schemas don’t turn empty strings to nils
(Form schemas do)
I’ve been thinking about changing that, it’s not gonna be pedantically correct, but it’d be very pragmatic
if you need more control over input and coercions, you can turn on explicit type specs, and define custom types where you need them
it’s gonna be more verbose but you’d get full control
DateOrNil = Types::Strict::Date.optional.constructor { |v|
v == '' ? nil : Types::Json::Date[v]
}
schema = Dry::Validation.JSON do
configure { config.type_specs = true }
required(:date, DateOrNil).maybe(:date?)
end
irb(main):038:0> schema.(date: '')
=> #<Dry::Validation::Result output={:date=>nil} errors={}>
irb(main):039:0> schema.(date: '2010-10-12')
=> #<Dry::Validation::Result output={:date=>#<Date: 2010-10-12 ((2455482j,0s,0n),+0s,2299161j)>} errors={}>