score:6
Accepted answer
Simply:
val originalA: A = // ...
val update: Update = // ...
val newA: A = A(
id = originalA.id,
a = update.a.getOrElse(originalA.a),
...
)
score:7
All case classes have a copy method.
http://docs.scala-lang.org/tutorials/tour/case-classes.html (find the copy term)
val a = A(1, "", "", "")
val update = Update(None, "scalaz".some, None)
val b = a.copy(
b = update.b.getOrElse(a.b)
)
Also check out the lens pattern for copying deeply nested objects in a functional manner:
http://eed3si9n.com/learning-scalaz/Lens.html
Once you have objects made up of other objects and so on, it becomes highly cumbersome to use the copy method. Scalaz's lens pattern implementation is a great alternative.
Source: stackoverflow.com
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