Support for type casts

[perotom]

It would be great if it is possible to support a custom binding symbol format. For example to generate the following statements with QueryDSL.

insert into message (type) values (cast(? as message_type))
or more postgresql specific
insert into message (type) values (?::message_type)

The would add great support for postgresql enums and other data types

[seratch]

How about doing like this? blog.seratch.net/post/76689657956/how-to-extend-scalikejdbc-querydsl (this URL is no longer available)

[sjurco]

How about doing like this:

package scalikejdbc

object SQLSyntaxParameterBinderFactory {
  def apply[T](syntax: T ⇒ SQLSyntax): ParameterBinderFactory[T] =
    (v: T) => SQLSyntaxParameterBinder(syntax(v))
}

must be in package scalikejdbc because SQLSyntaxParameterBinder is package private

object CustomType {
  implicit val customTypeParameterBinderFactory: ParameterBinderFactory[CustomType] =
    SQLSyntaxParameterBinderFactory(v ⇒ sqls"$v::custom_type")
}

just change custom_type and $v to make it work.

FYI: To read it back you need to define TypeBinder

  implicit val customTypeTypeBinder: TypeBinder[CustomType] = TypeBinder.string.map(CustomType.fromString)

Using this you can write just

insertInto(ClassWithCustomType).namedValues(autoNamedValues(c, ClassWithCustomType.column)

It could be done without custom Factory:

ParameterBinderFactory.sqlSyntaxParameterBinderFactory.contramap[CustomType](v ⇒ sqls"$v::custom_type")

but in this case contramap returns ContramappedParameterBinder which is not matched as SQLSyntaxParameterBinder in

scalikejdbc/scalikejdbc-core/src/main/scala/scalikejdbc/SQLInterpolationString.scala

Lines 39 to 53 in 535eb55

	private def addPlaceholders(sb: StringBuilder, param: Any): StringBuilder = param match {
	case _: String => sb += '?'
	case traversable: Traversable[_] => {
	// e.g. in clause
	traversable.map {
	case SQLSyntax(s, _) => s
	case SQLSyntaxParameterBinder(SQLSyntax(s, _)) => s
	case _ => "?"
	}.addString(sb, ", ")
	}
	case LastParameter => sb
	case SQLSyntax(s, _) => sb ++= s
	case SQLSyntaxParameterBinder(SQLSyntax(s, _)) => sb ++= s
	case _ => sb += '?'
	}

therefore simple question mark is used instead of custom sqls

@seratch could that be changed somehow so that anyone can define custom placeholder?

[seratch]

@sjurco Sorry for my belated reply. The solution you suggested looks fine. I welcome your pull requests to enable the new way.