make a lazy var in scala

Question

Scala does not permit to create laze vars, only lazy vals. It make sense.

But I\'ve bumped on use case, where I\'d like to have similar capability. I need a lazy var

Answer 1

You could simply do the compilers works yourself and do sth like this:

class Foo {
  private[this] var _field: String = _
  def field = {
    if(_field == null) {
      _field = "foo" // calc here
    }
    _field
  }

  def field_=(str: String) {
    _field = str
  }
}

scala> val x = new Foo
x: Foo = Foo@11ba3c1f

scala> x.field
res2: String = foo

scala> x.field = "bar"
x.field: String = bar

scala> x.field
res3: String = bar

edit: This is not thread safe in its currents form!

edit2:

The difference to the second solution of mhs is, that the calculation will only happen once, whilst in mhs's solution it is called over and over again.