Prepares a BSONReader that returns the result of applying f on the result of this reader.

import scala.util.Try
import reactivemongo.api.bson.{ BSONReader, BSONValue }

// Try to return an integer + 1,
// from any T that can be read from BSON
// and is a numeric type
def fromBSON[T](bson: BSONValue)(
  implicit r: BSONReader[T], n: Numeric[T]): Try[Int] = {
  val r2: BSONReader[Int] = r.afterRead { v => n.toInt(v) + 1 }
 r2.readTry(bson)
}

Prepares a BSONReader that transforms the input BSON value, using the given f function, before passing the transformed BSON value to the current reader.

import reactivemongo.api.bson.{
  BSONReader, BSONInteger, BSONNull, BSONString
}

val normalizingReader: BSONReader[Int] =
  implicitly[BSONReader[Int]].beforeRead {
    case BSONNull => BSONInteger(-1)
    case BSONString(s) => BSONInteger(s.size)
    // other values are unchanged
  }

normalizingReader.readOpt(BSONNull) // Some(-1)
normalizingReader.readTry(BSONString("foo")) // Success(3)
normalizingReader.readOpt(BSONInteger(4)) // unchanged: Some(4)

Tries to produce an instance of T from the bson value, returns None if an error occurred.

import reactivemongo.api.bson.{ BSONReader, BSONValue }

def fromBSON[T](bson: BSONValue)(implicit r: BSONReader[T]): Option[T] =
  r.readOpt(bson)

Tries to produce an instance of T from the bson value, returns the default value if an error occurred.

import reactivemongo.api.bson.{ BSONReader, BSONValue }

def fromBSON[T](bson: BSONValue, v: T)(implicit r: BSONReader[T]): T =
  r.readOrElse(bson, v)

Tries to produce an instance of T from the bson value.

import scala.util.Try
import reactivemongo.api.bson.{ BSONReader, BSONValue }

def fromBSON[T](bson: BSONValue)(implicit r: BSONReader[T]): Try[T] =
  r.readTry(bson)

Widen this read for compatible type U.

import reactivemongo.api.bson.BSONReader

val listReader: BSONReader[List[String]] =
  implicitly[BSONReader[List[String]]]

val widenAsSeqReader: BSONReader[Seq[String]] =
  listReader.widen[Seq[String]]
  // as Seq[String] >: List[String]