Question

Is there a way to make a copy of an object (or even better a list of objects)? I m talking about custom objects of classes that may be extended by other classes.

例如:

class Foo() {
   var test = "test"
}

class Bar() extends Foo {
   var dummy = new CustomClass()
}

var b = new Bar()
var bCopy = b.copy() // or something?

Answer 1

在 Java,他们试图通过在所有超级阶级中援引<代码>clone的方法解决该问题,但一般认为这种做法是破碎的,最好加以避免,原因如下:http://www.artima.com/intv/bloch13.html”。

So in Scala, as genereally in Java, you will have to make your own copy method for an arbitrary class, which will allow you to specify things like deep vs shallow copying of fields.

If you make you class a case class, you get a copy method for free. It s actually better than that, because you can update any of the fields at the same time:

case class A(n: Int)
val a = A(1)         // a: A = A(1)
val b = a.copy(a.n)  // b: A = A(1) 
val c = a.copy(2)    // c: A = A(2)

However inheriting from case classes is deprecated.

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