Is it possible to extend a method within an extended scala class?

Question

Assume I have the following scala classes, is it possible to extend a function on SecondClass and add more code to it? (possibly chained to another function within the function i'd like to extend)

package io.gatling.http.check
class FirstClass {

  def login() = {
    exec(http("Login")
      .post("anonymous/login")
      .body(ElFileBody("rest/UserAnonymousLogin.json")).asJson
}
}

I would like to extend the login function with the following (.check(status is 200)

class SecondClass extends FirstClass {

  def login() = {
     .check(status is 200))
}
}

Is that possible?

Answer 1

Given checks method accepts a variable number of HttpCheck, that is, HttpCheck*

def check(checks: HttpCheck*): HttpRequestBuilder

consider refactoring FirstClass to

  class FirstClass {
    def login(checks: HttpCheck*) = {
      exec(http("Login")
        .post("anonymous/login")
        .body(ElFileBody("rest/UserAnonymousLogin.json")).asJson
        .check(checks: _*)
      )
    }
  }

Note how by default we pass no checks when calling (new FirstClass).login().

Now derived classes could pass in a checks to be performed like so

  class SecondClass extends FirstClass {
    def loginWithStatusCheck() = {
      super.login(status is 200)
    }
  }

Note we are not actually overriding FirstClass.login here.

Another approach instead of overriding could be functional composition, for example, we break down the problem into smaller functions

  val buildClient: String => Http = http(_)
  val buildPostRequest: Http => HttpRequestBuilder = _.post("anonymous/login").body(ElFileBody("rest/UserAnonymousLogin.json")).asJson
  val checkStatus: HttpRequestBuilder => HttpRequestBuilder = _.check(status is 200)

and then compose them

exec((buildClient andThen buildPostRequest andThen checkStatus)("Login"))

Now we can simply add further steps to the composition instead of worrying about class hierarchies and overriding.