Reassigning to val on initialization in main constructor
class Person(){
val name : String
def this(n : String) {
this()
this.name = n
}
}
compile time error : reassignment to val
I am new to scala and so far I have learned how to use primary constructor and case classes to initialize data members. I'm just wandering if there is a way to initialize the val data item inside this . Initializing var item works fine: -
class Person(){
var name : String = _
def this(n : String) {
this()
this.name = n
}
}
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You just can't assign val after initialization. In Scala, the body of the IS class is a constructor, you can see examples here .
In general, you just define all the variables in the main constructor as "class parameters": class Person(val name: String)
if you need to get a name for initialization, or class Person() { val name = 'Joe' }
if it's fixed.
This can be quite unexpected from Java, since you are used to having constructors that produce values and create an object directly. In such a case, the best solution is to use the application methods at the accompanying object:
class Person(val name: String)
object Person() {
def apply(db: SomeDBConnectionWrapper, id: Int) = new Person(db.fetchName(id))
}
This allows you to call Person(db, 3)
to get a new person with custom initialization, but the constructor itself still gets everything it needs to create a new instance where all the values are assigned only once.
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