Using class parameters to assign field value

Question

I'm new to scala and would like to use class parameters to assign the value to a field of the same. In Java, we do similar thing within a constructor:

public class Test{

    private final int value;

    public Test(int value){
        this.value = value;
    }
}

Now, I tried to do a similar thing in Scala:

class Test(value: Int){
   val value = ..WHAT..value //Is there a way to assign a parameter value to a field with the same name?
}

object Test{
   def testMethod = //access value and do something with it.
}

Can we do something similar to what we can in do in Java?

Possible duplicate of How do I expose Scala constructor arguments as public members? — Tzach Zohar
– Tzach Zohar, Commented Aug 23, 2016 at 8:13

Tzach Zohar · Accepted Answer · 2016-08-23 08:21:29Z

1

Scala provides a shorter syntax for creating such a member - just add the keyword val before the argument name in the class parameter list. You can also add a modifier (e.g. private):

scala> :paste
// Entering paste mode (ctrl-D to finish)

class Test(private val value: Int)

object Test {
  def testMethod(t: Test) = t.value
}

// Exiting paste mode, now interpreting.

defined class Test
defined module Test

scala> Test.testMethod(new Test(5))
res1: Int = 5

edited Aug 23, 2016 at 8:21

answered Aug 23, 2016 at 8:12

Tzach Zohar

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3 Comments

user3663882 Over a year ago

AFAIK, it will make it a public member. As a Java programmer, we don't quite like making class members be public. Is it common in Scala?

TheKojuEffect Over a year ago

@user3663882 Scala follows Uniform Access Principle. Check out.joelabrahamsson.com/learning-scala-part-nine-uniform-access

user3663882 Over a year ago

Huh, didn't think that we can declare such things. Thank you.

sebszyller · Accepted Answer · 2016-08-23 08:25:27Z

1

If you don't like exposing a private member, you could go for this:

class A {
  private var _quote = ""
  def quote = _quote
  def quote_=(newQuote: String) = _quote = newQuote
}

Which would you give you a getter and setter, both accessible by calling quote.

answered Aug 23, 2016 at 8:25

sebszyller

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1 Comment

jwvh Over a year ago

You can also make that private var, with its default value, an optional constructor parameter.

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