Functional Programming: This thread is like a burrito

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > Functional Programming: This thread is like a burrito

Good Will Hrunting: Oct 8, 2012; I changed my mind.
I'm not sorry.

Could use some help in going from my comfortable OOP/imp Java style to Scala functional style. Basically, I have a stream of events coming in, all of which are one of a set of discrete types, and for every type we would like to have a set of "enhancement" functions executed based on the type. In Java, I'd probably just have created an "Event" class and extended that for each of the events, keeping a set of implementations of an "enhancer" function and overriding the "enhance" function in each Event extensions with the execution of all of the enhancers kept in that Set. I'm struggling a bit with how to structure this "properly" with Scala. Obviously I could probably implement it very similarly to how I did it in Java, but I don't know if that's the best method.

On a similar note, while picking up syntax and understanding what's going on behind the scenes of Scala -> JVM code, picking up the functional paradigms has been hard for me.

# ¿ Mar 23, 2017 15:14

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# ¿ May 14, 2024 14:38

Good Will Hrunting: Oct 8, 2012; I changed my mind.
I'm not sorry.

Everything could return the same event type. Basically I need to turn a JSON record like {eventType, timestamp, key} into {eventType, timestamp, key, enhancement1, enhancement2, enhancement3} where those "enhancements" are just results of running the enhancement functions which range from a few calculations to lookups in local files.

# ¿ Mar 23, 2017 15:39

Good Will Hrunting: Oct 8, 2012; I changed my mind.
I'm not sorry.

Is "cake pattern" the only way to mock out something like this? I need to mock out MaxmindDatabases.getConnectionTypeResult in a unit test but you can't mock objects. I guess another option is to create a companion object of the class and access it like that? I'm brand new to Scala so I really can't evaluate tradeoffs of such things too well.

code:

object MaxmindDatabases {
  lazy val CONNECTION_TYPE_READER: DatabaseReader = initializeDb(ConnectionTypeFile.fileName)

  def getConnectionTypeResult(ipAddress: InetAddress): ConnectionTypeResponse = {
    CONNECTION_TYPE_READER.connectionType(ipAddress)
  }

  def initializeDb(mmdbFile: String): DatabaseReader = {
    //bunch of useless crap
  }
}

# ¿ Mar 29, 2017 22:26

Good Will Hrunting: Oct 8, 2012; I changed my mind.
I'm not sorry.

I'm half asleep right now so I'll give this a shot tomorrow but I think the thing tripping me up was that a few things I was trying to mock were Objects which can't be mocked as easily as classes. I have a parent class that has a function with an arbitrary number of Objects being called and those functions don't really make sense as classes because they'll never have any non-instance properties or anything so I made them Scala objects. I guess I could change everything to classes, expose via companion, and mock accordingly.

# ¿ Mar 30, 2017 06:04

Good Will Hrunting: Oct 8, 2012; I changed my mind.
I'm not sorry.

What's the most efficient way in Scala to do pass a String through a number of possible regex pattern and match based on which pattern is matched?

code:

  val A: Regex = "([^/]+)/([.0-9]+) \\((iPhone|iPad); iOS ([.0-9]+); Scale/[.0-9]+\\)".r
  val B: Regex = "(69 420 gains)".r

  def resolveCustomRegex(ua: String): Data = {
    ua match {
      case A => //need the captured groups here
      case B => //need the captured groups here
    }
  }

This seems like it would be less efficient than piping the two together like ([^/]+)/([.0-9]+) \\((iPhone|iPad); iOS ([.0-9]+); Scale/[.0-9]+\\) | (69 420 gains) but in the second case capturing match groups doesn't seem feasible. Also I can't figure out how to get the groups in each case's corresponding function

# ¿ Jun 19, 2017 19:08

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