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extending multiple traits.

1 reply on 1 page. Most recent reply: Feb 2, 2008 1:21 AM by Eric Willigers

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jeroen dijkmeijer

Posts: 6
Nickname: 53764
Registered: Jan, 2008

extending multiple traits. Posted: Feb 1, 2008 6:47 AM
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I'm currenlye reading the book, its well written and a pleasure to read. I do have a question though on page 74 (not sure which version) the book says:
In Java, a class can implement zero to many interfaces. Similarly in Scala, a class can extend zero to many traits;
But how you can implement multiple traits is not discussed. Or is the "with mix in" meant, I dont see that as a multiple implements.

regards,
Jeroen.


Eric Willigers

Posts: 8
Nickname: ewilligers
Registered: Dec, 2007

Re: extending multiple traits. Posted: Feb 2, 2008 1:21 AM
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In

trait A { def f = 42 }
trait B { def g = false }
trait C { def h = "answer" }
class ABC extends A with B with C {}

you can optionally change A to being a class, and you can also optionally change ABC to being a trait or object.

So we use "extends" before the first class or trait that we wish to inherit from, and if we wish to inherit from additional traits, we use "with" before each of them.

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