Effective Scala, part 8 - OO concepts

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Flip the perspective on tools like interfaces and traits. Don't see them as a way for objects to share an interface, but as an abstraction over implementations.

So, not: DatabaseAccess -> (InMemoryDatabase, PhysicalDatabase)

but: DatabaseAccess <- (InMemoryDatabase, PhysicalDatabase)

An interface is more usefully seen as:

- DatabaseAccess creates an abstraction barrier so we can ignore which database is used underneath

than as:

- DatabaseAccess allows various databases to share the interface.

The former encourages the view/use of interface as an abstraction over implementation.

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