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

Sedro: Dec 31, 2008

Lumpy posted:

As someone just starting to look into functional programing, which ones are the "impure" ones? Why are they only "functional-ish"? Why should I avoid them?

If we only included pure languages this would be a haskell thread

# ¿ May 1, 2015 19:33

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# ¿ Apr 28, 2024 22:13

Sedro: Dec 31, 2008

For the most Robust, Scalable Enterprise Solution you should use a time service. http://www.timeapi.org/utc/mon?format=%25A

# ¿ Sep 17, 2015 18:59

Sedro: Dec 31, 2008

Good Will Hrunting posted:

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.

I don't think the cake pattern will help here. If you're new to scala, you're better off pretending the cake pattern doesn't exist.

The solution is the same as other languages:
1. Create a trait (interface) containing the public API
2. Accept an instance of the trait instead of referencing the singleton object
3. Use a mock implementation in your tests

code:

trait DatabaseConnection {
  def getConnectionTypeResult(ipAddress: InetAddress): ConnectionTypeResponse
}

object MaxmindDatabases extends DatabaseConnection {
  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
  }
}

class ThingThatUsesDatabase(dbs: DatabaseConnection)

// prod:
new ThingThatUsesDatabase(MaxmindDatabases)

// test:
new ThingThatUsesDatabase(new DatabaseConnection { /* mock stuff */ })

# ¿ Mar 30, 2017 05:44

Sedro: Dec 31, 2008

Beamed posted:

Does Twitter use Scala anymore? IIRC they started moving away from it at some point.

They're still using it

# ¿ Jul 23, 2017 03:37

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