Auto Macros

Avoid Boilerplate Code

You can avoid writing boilerplate code when using scalikejdbc-syntax-support-macro.

Setup

Add the following aditional dependency to your sbt project.

libraryDependencies += "org.scalikejdbc" %% "scalikejdbc-syntax-support-macro" % "4.2.1"

Usage

autoConstruct for extracting entities from ResultSet

Usually, we should write ResultSet extractor method as follows.

case class Company(id: Long, name: String, countryId: Option[Long], country: Option[Country] = None)

object Company extends SQLSyntaxSupport[Company] {

  def apply(rs: WrappedResultSet, rn: ResultName[Company]): Company = new Company(
    id = rs.get(rn.id), 
    name = rs.get(rn.name), 
    countryId = rs.get(rn.countryId)
  )
}

When using scalikejdbc-syntax-support-macro, you can use #autoConstruct macro.

case class Company(id: Long, name: String, countryId: Option[Long], country: Option[Country] = None)

object Company extends SQLSyntaxSupport[Company] {

  def apply(rs: WrappedResultSet, rn: ResultName[Company]): Company = 
    autoConstruct(rs, rn, "country") // "country" will be ignored when binding values from ResultSet
}

The #autoConstruct method binds all the fields defined at the primary constructor automatically.

The country field in the above example class should be ignored. In such cases, you should specify additional String parameter such as "country". Of course, the "country" will be verified at Scala compilation time. We believe that’s pretty cool and useful.

autoColumns to avoid accessing JDBC metadata

When your code load ScalikeJDBC DAO objects, ScalikeJDBC automatically fetches all the column names for the table specified by SQLSyntaxSupport’s tableName (via JDBC metadata API).

If you don’t prefer the behavior, you can choose loading column names from the entity class’s field names instead. The following code won’t access JDBC metadata and will resolve column names from Company class’s fields, primary constructor’s parameters, by simply converting them to snake-cased ones or applying nameConverters to them.

case class Company(id: Long, name: String, countryId: Option[Long], country: Option[Country] = None)

object Company extends SQLSyntaxSupport[Company] {

  override lazy val columns = autoColumns[Company]("country") 
  // this will be Seq("id", "name", "country_id")
}