Application Architecture - Uncle Bob

Question

One week ago I've watched Robert C. Martin presentation about architecture: http://www.youtube.com/watch?v=WpkDN78P884

I don't understand the chart which you could see at 0:24:46. I was trying to implement it, but some how I can't. Why there are 2 boundries? Why Delivery mech. implements Boundry? Im confused, could anyone explain it to me?

Best regards

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EDIT: ok, I've found the answer

Answer 1

The boundries would be repesented by interfaces in .NET. What he is showing is the interactor can expose multiple interfaces. There could be only one, there could be more that 2. The number would be dicated by the application and what the interactor was exposing. The boundries serve as the method to get data in and out of the interactor. A boundry would be a set of methods invoked by the interactor or the display layer.

Answer 2

You might have a boundary representing the Communications Channel, with which a Web Application (like a Rails Controller) might deal with an interactor to handle business logic for a web request. You might have a boundary representing a data repository, with which an ORM might interact with an interactor to fetch data from a database and map the query result to attributes for an entity. You might have a boundary representing a mailer gateway, which the interactor might interact with to initiate sending a mail message. The mailer, ORM and web application all live on the other side of the boundary, and interact with the application in large part through the boundaries.