Question

I have the following code:

private def hasRole(role: String): Boolean = {
  var hasRole = false;
  if(getUserDetails.isDefined){

    // getAuthorities returns java.util.Collection<GrantedAuthority>
    val authorities: util.Collection[_ <:GrantedAuthority] = getUserDetails.get.getAuthorities
    // Wrap the collection is a Scala class 
    val authoritiesWrapper = JCollectionWrapper.apply(authorities);
    for(authority <- authoritiesWrapper.iterator){
      if(authority.getAuthority == role){
        hasRole = true;
        scala.util.control.Breaks.break  
      }
    }
  }
  hasRole
}

The question is, is scala.util.control.Breaks.break the correct way toreturn when I’ve found the role? Doesn’t look right to me.

Answer 1

If you want to use breakable, you need to do it like so:

import scala.util.control.Breaks._
breakable {
  for (i <- 0 to 10000) { if (i>3) break }
}

But if you find yourself doing that often, you’re probably not using the collections library to its full extent. Try instead

authoritiesWrapper.iterator.exists(_.getAuthority == role)

Also, in the example you gave, you could also

if (authority.getAuthority == role) return true

When to choose which? In general, you should use the control-flow options in the collections library if you can. They generally are the fastest and clearest. Wait, fastest–why is that? Both break and return (from within a for or other context that requires a closure–basically anything but if and while and match) actually throw a stackless exception which is caught; in the break case it’s caught by breakable and in the return case it’s caught by the method. Creating a stack trace is really slow, but even stackless exceptions are kind of slow.

So using the correct collections method–exists in this case–is the best solution.