Returning "object" in scala

Question

I'm kinda new to scala. I got into trouble while trying to return object type.

Here is the code.

It shows "error: not found: type A"

object A{}

object B {
  def getInstance() : A = {
    return A
  }
}

If I do similar kind of thing with class instance, it wont show any problem.

class A{}

object B {
  def getInstance() : A = {
    return new A
  }
}

As far as I know object type is a singleton instance of class. What am I missing here?

DwB · Accepted Answer · 2013-11-22 14:26:19Z

4

Compiler complains that can not find type A because in your case A is a name of an object not a type, use A.type to refer to type, like this:

object A

object B {
  def getInstance: A.type = A
}

DwB

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answered Nov 22, 2013 at 13:10

grotrianster

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1 Comment

Just would like to add that with type inference you could actually omit return type and write just def getInstance = A

flavian · Accepted Answer · 2013-11-22 13:07:57Z

3

Because object is a singleton is does not define a type, instead in defines a value.

If you would look at the Java equivalent, using scala object produces the:

A$ class //
A$.MODULE$ // singleton instance definition

The type is however masked and can be accessed via A.type.

Using return is also not necessary in Scala. The last statement position in a block is automatically interpreted as return value.

class A{}

object B {
  def getInstance() : A = new A
}

answered Nov 22, 2013 at 13:07

flavian

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