calasql-core_3.0.1.9.source-code.JoinNullable.scala Maven / Gradle / Ivy
package scalasql.core
import scalasql.core.SqlStr.SqlStringSyntax
/**
* Represents a set of nullable columns that come from a `LEFT`/`RIGHT`/`OUTER` `JOIN`
* clause.
*/
trait JoinNullable[Q] {
def get: Q
def isEmpty[T](f: Q => Expr[T])(implicit qr: Queryable[Q, ?]): Expr[Boolean]
def nonEmpty[T](f: Q => Expr[T])(implicit qr: Queryable[Q, ?]): Expr[Boolean]
def map[V](f: Q => V): JoinNullable[V]
}
object JoinNullable {
implicit def toExpr[T](n: JoinNullable[Expr[T]])(implicit mt: TypeMapper[T]): Expr[Option[T]] =
Expr { implicit ctx => sql"${n.get}" }
def apply[Q](t: Q): JoinNullable[Q] = new JoinNullable[Q] {
def get: Q = t
def isEmpty[T](f: Q => Expr[T])(implicit qr: Queryable[Q, ?]): Expr[Boolean] = Expr {
implicit ctx =>
sql"(${f(t)} IS NULL)"
}
def nonEmpty[T](f: Q => Expr[T])(implicit qr: Queryable[Q, ?]): Expr[Boolean] = Expr {
implicit ctx =>
sql"(${f(t)} IS NOT NULL)"
}
def map[V](f: Q => V) = JoinNullable(f(t))
}
}