scala case class default argument

Question

I faced the following definition in some source code:

case class Task(uuid: String = java.util.UUID.randomUUID().toString, n: Int)

Here the first argument declared with default value, but I don't understand how to create instance with this default value. If I can not pass the first argument like Task(1) then I certainly get compilation error.

However the following change works fine:

case class Task(n: Int, uuid: String = java.util.UUID.randomUUID().toString)

But here, as showed in the definition, uuid is a first argument.

sarveshseri · Accepted Answer · 2018-01-30 10:41:36Z

8

In Scala functions, whenever you omit a parameter (for a default value), all the following parameters (if provided) are required to be provided with names.

So, if you gave a function like following,

def abc(i1: Int, i2: Int = 10, i3: Int = 20) = i1 + i2 + i3

You can use it in following ways,

abc(1)

abc(1, 2)

abc(1, 2, 3)

But if you want to use default value of i2 and provide a value for i3 then,

abc(1, i3 = 10)

So, in your case, you can use it like following,

val task = Task(n = 100)

answered Jan 30, 2018 at 10:41

sarveshseri

14k30 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sergii Lagutin · Accepted Answer · 2018-01-30 10:40:17Z

3

If you have Task class defined like this case class Task(uuid: String = java.util.UUID.randomUUID().toString, n: Int), you may create new instance only with n argument in such way:

Task(n = 1)

answered Jan 30, 2018 at 10:40

Sergii Lagutin

10.7k1 gold badge37 silver badges44 bronze badges

Comments

o-0 · Accepted Answer · 2018-01-30 11:10:22Z

1

The important point here is: If you have a class/method definition that take n parameters but you need pass to only 1 to n-1 arguments; you use the name of the arguments with = sign and then the value of the argument you want to pass on, so in your case:

val task = Task(n=2)

answered Jan 30, 2018 at 11:10

o-0

1,79914 silver badges30 bronze badges

Collectives™ on Stack Overflow

scala case class default argument

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related