How to write rule for validating collections?

case class Customer(id: Int, name: String)

case class CustomerCollection(customers: Vector[Customer])

implicit val customerValidator: AsyncValidator[CustomerCollection] =
    AsyncValidator[CustomerCollection]
.async.rule(_.customers, ....)

[krzemin]

That’s the point - you don’t need to write rules for collections manually.

import octopus.dsl._
import octopus.syntax._

case class Customer(id: Int, name: String)
case class CustomerCollection(customers: Vector[Customer])

implicit val cutsomerValidator: Validator[Customer] = Validator[Customer]
  .rule(_.name, (_: String).trim.nonEmpty, "name must not be empty")

val customers = CustomerCollection(Vector(Customer(1, "C1"), Customer(2, "   "), Customer(3, "")))
customers.validate
// invalid:
//  customers[1].name: name must not be empty
//  customers[2].name: name must not be empty

Octopus will derive rules for collection automatically!

However sometimes you may want to additionally restrict collection itself. In this case you can define your own rules and compose with derived ones:

implicit val customerCollectionValidator: Validator[CustomerCollection] = Validator[CustomerCollection]
  .derived
  .rule(_.customers, (_: Vector[Customer]).length % 2 == 0, "number of customers must be even")

customers.validate
// invalid:
//  customers[1].name: name must not be empty
//  customers[2].name: name must not be empty
//  customers: number of customers must be even

Intentionally this should work equally well for asynchronous validators.

[pixime]

It seems that works better like this:

    implicit val customerCollectionValidator: Validator[CustomerCollection] = Validator[CustomerCollection]
      .rule(_.customers, (_: Vector[Customer]).length % 2 == 0, "number of customers must be even")
      .composeDerived