Scala 中的特征和抽象方法覆盖
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Traits and abstract methods override in Scala
提问by IttayD
I have a base abstract class (trait). It has an abstract method foo(). It is extended and implemented by several derived classes. I want to create a trait that can be mixed into the derived classes so that it implements foo()and then calls the derived class's foo().
我有一个基本抽象类（特征）。它有一个抽象方法foo()。它由几个派生类扩展和实现。我想创建一个可以混合到派生类中的特征，以便它实现foo()然后调用派生类的foo().
Something like:
就像是：
trait Foo {
def foo()
}
trait M extends Foo {
override def foo() {
println("M")
super.foo()
}
}
class FooImpl1 extends Foo {
override def foo() {
println("Impl")
}
}
class FooImpl2 extends FooImpl1 with M
I tried self types and structural types, but I can't get it to work.
我尝试了自我类型和结构类型，但我无法让它工作。
回答by retronym
You were very close. Add the abstract modifier to M.foo, and you have the 'Stackable Trait' pattern: http://www.artima.com/scalazine/articles/stackable_trait_pattern.html
你非常接近。将抽象修饰符添加到 M.foo，您将拥有“可堆叠特征”模式：http: //www.artima.com/scalazine/articles/stackable_trait_pattern.html
trait Foo {
def foo()
}
trait M extends Foo {
abstract override def foo() {println("M"); super.foo()}
}
class FooImpl1 extends Foo {
override def foo() {println("Impl")}
}
class FooImpl2 extends FooImpl1 with M
