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    <p>Yes, this is absolutely fine approach. And yes, sometimes you can use constructor injection, nothing wrong with that too. But with constructor injection you have to propagate your dependencies <em>manually</em>, while with cake pattern your dependencies are propagated <em>automatically</em> via self-type annotations. So for big projects constructor injection actually lead to more boilerplate than cake pattern, especially at the construction site (where you create all your objects and set up dependencies between them).</p> <p>However, what you have presented is not full-fledged cake pattern. In real cake pattern there is an additional layer around business logic classes, so-called components, and you do not wire up logic classes directly but components instead.</p> <pre><code>trait FileStorageComponent { def fileStorage: FileStorage trait FileStorage { def readFile(filename: String): OutputStream } } trait S3FileStorageComponent extends FileStorageComponent { val fileStorage = new S3FileStorage class S3FileStorage extends FileStorage { def readFile(filename: String): OutputStream = ??? } } trait FileHttpServerComponent { self: FileStorageComponent =&gt; val fileHttpServer = new FileHttpServer class FileHttpServer { def fetchFile(session: Session, filename: String) = ??? } } // Wiring object S3FileHttpServer extends FileHttpServerComponent with S3FileStorageComponent // Anonymous val server = new FileHttpServerComponent with S3FileStorageComponent // Mocking object TestFileHttpServer extends FileHttpServerComponent with FileStorageComponent { val fileStorage = mock[FileStorage] } </code></pre> <p>In this approach there are more boilerplate in traits definitions, but in return you have greater flexibility and very clear dependency management on the use place. For example, here is how program entry point in one of my projects looks like:</p> <pre><code>object Main extends MainUI with DefaultActorsManagerComponent with DefaultPreferencesAccessComponent with DefaultModelComponent with DefaultMainWindowViewComponent with DefaultMainWindowControllerComponent with MainWindowReporterComponent with DefaultClientActorComponent with DefaultResponseParserActorComponent with DefaultArchiverActorComponent with DefaultMainWindowAccessActorComponent with DefaultUrlParserComponent with DefaultListenerActorComponent with DefaultXmlPrettifierComponent </code></pre> <p>All main program components are in one place. Pretty neat IMO.</p>
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    1. POAbstract fields for dependency injection
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    1. USVladimir Matveev
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    1. COThanks. My wording was a bit off - am aware my example code wasn't cake pattern, but wanted to clarify if using inheritance on abstract members as a form of injection was an acceptable thing to do for simple use cases with fairly flat dependency trees where Cake (or a service locator) might be a bit heavy.
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      1. USJames Davies
 

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