Scala: Initialize Object with External Parameters

Question

Assume I have a variable x which receives its value from the user at some point. Once that is done, I need to set up an Object which needs the value of x.

Naively, I'd like to write:

Object MyCoolObject(num:Double) {
  //code
}

and then somewhere in the code:

val MCO = MyCoolObject(x)

But that's not possible in Scala. So how do I do it?

I think you will need to dig around companion object and apply method. — Pavel
– Pavel, Commented Mar 21, 2016 at 9:04
It looks like everyone here is pretty confused about this question - maybe you should back up a bit and explain at a higher lever what you're trying to accomplish, and give some additional context? Otherwise I think the answer to the exact question you've presented so far is simply that it isn't possible to parameterize an object. — Chris Martin
– Chris Martin, Commented Mar 21, 2016 at 9:52

Community · Accepted Answer · 2017-05-23 11:59:30Z

1

This is already discussed here: Pass Parameters to Scala Object

You can also use a case class:

  case class MyCoolObject(num: Double)
  {
    //code
  }


  val n = 10 // external data
  val myCoolObject = MyCoolObject(n)

edited May 23, 2017 at 11:59

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answered Mar 21, 2016 at 9:07

tuxdna

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2 Comments

shakedzy Over a year ago

Thanks, but not what I'm looking for - I need to keep it as an object and not a class. also, the MongoDB way to do so is not what I have here. It's really is about passing a parameter, like n in your example

tuxdna Over a year ago

You have some misunderstanding of how Scala objects are created. Please read the duplicate question link I shared.

Pavel · Accepted Answer · 2016-03-21 09:13:06Z

0

Something like this:

class MyCoolObject(num:Double) {    
}

object MyCoolObject{
    def apply(x:Double) = new MyCoolObject(x)
}

val x : Double = 56.1
val MCO = MyCoolObject(x)

You can use this article i.e. https://twitter.github.io/scala_school/basics2.html

edited Mar 21, 2016 at 9:13

answered Mar 21, 2016 at 9:06

Pavel

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5 Comments

shakedzy Over a year ago

How do I call it? val MCO = Bar(x)? Will MCO hold the object or the class?

Pavel Over a year ago

Just amended answer with proper code for you need. MCO will hold new instance of the class.

shakedzy Over a year ago

Is there any way to this with MCO still being an object and not an instance of a class?

Pavel Over a year ago

Well, I would say yes. Not sure why you need this. But I would do something like: object MyCoolObject{ var myValue : Double = 0 def apply(x: Double) = { myValue = x this } }

Pavel Over a year ago

You will store you value in the companion object. Try do println ( MCO.myValue) .

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