Overriding Traits During Instantiation

13 March 2015 - Redwood City

You can create a base trait with concrete methods which will be used in a class only to override that class with a different trait on impliementation.

For example:

trait Logger {
  def log(message: String) { }  // a concrete implimentation
}

Used in a class definition:

class CustomerAnalytics extends Analytics with Logger {
  def foo(input: Double) {
    if (input > max) log("Insufficient funds")
    // ...
  }
  // ...
}

Now inherit from that trait:

trait ConsoleLog extends Logger {
  override def log(msg: String) { println(msg) }
}

trait LogglyLog extends Logger {
  override def log(msg: String) {
    //... use the loggly service
  }
}

And on instantiation, use whichever trait fits the situation best:

val analysis0 = new CustomerAnalytics with ConsoleLog
val analysis1 = new CustomerAnalytics with LogglyLog