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authorAndy <andys8@users.noreply.github.com>2017-07-04 20:21:45 +0200
committerven <vendethiel@hotmail.fr>2017-07-04 20:21:45 +0200
commit84c35749189d0d9d9f5b72036dd47780c41bf7c7 (patch)
tree69c38ec2122dda8cd798f377d80a45934ad2f11e /scala.html.markdown
parent362135e6bc78a48acb8610b9956d87193680c5cb (diff)
[scala/en] Add traits in objects chapter (#2760)
* [scala/en] Add traits in objects chapter * [scala/en] Traits: Describe traits keywords
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1 files changed, 45 insertions, 1 deletions
diff --git a/scala.html.markdown b/scala.html.markdown
index 5eb94986..78053b40 100644
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+++ b/scala.html.markdown
@@ -460,8 +460,52 @@ val otherGeorge = george.copy(phoneNumber = "9876")
// And many others. Case classes also get pattern matching for free, see below.
+// Traits
+// Similar to Java interfaces, traits define an object type and method
+// signatures. Scala allows partial implementation of those methods.
+// Constructor parameters are not allowed. Traits can inherit from other
+// traits or classes without parameters.
+
+trait Dog {
+ def breed: String
+ def color: String
+ def bark: Boolean = true
+ def bite: Boolean
+}
+class SaintBernard extends Dog {
+ val breed = "Saint Bernard"
+ val color = "brown"
+ def bite = false
+}
+
+scala> b
+res0: SaintBernard = SaintBernard@3e57cd70
+scala> b.breed
+res1: String = Saint Bernard
+scala> b.bark
+res2: Boolean = true
+scala> b.bite
+res3: Boolean = false
+
+// A trait can also be used as Mixin. The class "extends" the first trait,
+// but the keyword "with" can add additional traits.
+
+trait Bark {
+ def bark: String = "Woof"
+}
+trait Dog {
+ def breed: String
+ def color: String
+}
+class SaintBernard extends Dog with Bark {
+ val breed = "Saint Bernard"
+ val color = "brown"
+}
-// Traits coming soon!
+scala> val b = new SaintBernard
+b: SaintBernard = SaintBernard@7b69c6ba
+scala> b.bark
+res0: String = Woof
/////////////////////////////////////////////////