CustomKeys.md

Custom Keys

The key types that are supported by default are String and java.lang.Long. If your EntityFormat uses anything other than these two types you will need to provide an implicit ToKey[A] for your format. For example:

import com.ovoenergy.datastore4s._
import com.google.cloud.datastore.Key

object CustomKeyExample {
  
  case class Employee(name: String, age: Int, department: String)
  
  case class CustomKey(name: String, department: String)

  implicit object CustomToKey extends ToKey[CustomKey] {
    override def toKey(value: CustomKey, keyFactory: KeyFactory): Key = 
      keyFactory.buildWithName(s"${value.name}@${value.department}")
  }
  
  implicit val format = EntityFormat[Employee, CustomKey]("employees")(e => CustomKey(e.name, e.department))
}

There is also a utility function in DatastoreRepository called toKey[A] that allows you to simply pass a function, for example:

implicit val customToKey = toKey[CustomKey]((value, keyFactory) => keyFactory.buildWithName(s"${value.name}@${value.department}"))

Ancestors

To use ancestors in keys and queries create an implicit ToAncestor[A] for your types using the toStringAncestor or toLongAncestor function. For example:

import com.ovoenergy.datastore4s._
import com.google.cloud.datastore.Key

case class Department(name: String)

object AncestorExample extends DatastoreRepository {
    
  // Provide the name of the kind and a function A => String (Or A => Long in the case of a LongAncestor)
  implicit val departmentAncestor = toStringAncestor[Department]("Department")(_.name)
  
  case class CustomKey(name: String, department: Department)
  
  implicit val customToKey = toKey[CustomKey]((value, keyFactory) =>
      keyFactory.addAncestor(value.department).buildWithName(value.name))
}