Scala: Partially applied functions

Question

I am relatively new to Scala, and just trying to get my head around the use of partially applied functions to solve my problem.

My problem is that in my code I have the following foreach logic in multiple places:

for (teamType <- TeamType.allTypes) {
  findViewById(teamType.layoutID).findViewById(buttonID)
    .setOnClickListener(matchButtonOnClickListener)
}

and again here:

for (teamType <- TeamType.allTypes) refreshTeamStatisticViews(teamType)

Basically, for each teamType in the TeamType case object, I am looking to perform a function that returns Unit

What I was thinking of doing is moving the foreach part into the TeamType case object, and then have that take a function or partially applied function that returns Unit.

So for example, TeamType would contain the following:

def forAllTeamTypes(fun: TeamType => Unit) = for(teamType <- allTypes) fun(teamType)

and for the second example above, I could change it to

TeamType.forAllTeamTypes(refreshTeamStatisticViews)

However, I am not sure how to apply this for partially applied functions for the more complex first example.

Can someone help me?

senia · Accepted Answer · 2013-05-27 19:13:55Z

2

Short answer:

TeamType.forAllTeamTypes{ teamType =>
  findViewById(teamType.layoutID).findViewById(buttonID).setOnClickListener(matchButtonOnClickListener)
}

Let's look at your code:

for (teamType <- TeamType.allTypes) {
  findViewById(teamType.layoutID).findViewById(buttonID).setOnClickListener(matchButtonOnClickListener)
}

it actually means this:

TeamType.allTypes.foreach{ teamType =>
  findViewById(teamType.layoutID).findViewById(buttonID).setOnClickListener(matchButtonOnClickListener)
}

foreach method takes TeamType => Unit as parameter, just like your method forAllTeamTypes.

answered May 27, 2013 at 19:13

senia

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Comments

Heptic · Accepted Answer · 2013-05-27 19:05:14Z

1

You would probably be better off using the built in functions. It would seem like .foreach already has the signature you want.

It will look something like:

TeamType.allTypes.foreach (functionOfYourChoosing)

answered May 27, 2013 at 19:05

Heptic

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2 Comments

DJ180 Over a year ago

My TeamType is actually a case object, and not an enum. I should have clarified this

Heptic Over a year ago

In there you could define a member allTypes that was a List[TeamType] ? Or something. It's hard to judge without a more minimal and complete example :D

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