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Contents
The _service locator_ design pattern can be considered a subset of dependency injection. Because it is simpler, it is as good of a place to start teaching DI as any. To demonstrate both techniques, we'll pretend we're going to write an online forum application. To start, let's come up with a rough design by cataloging the components we'll need. * @Logger@. This will be used to write messages to a file. * @Authenticator@. This will be used to validate whether a user is who they say they are. * @Database@. This encapsulates access to the database that will store our forum data. * @Session@. This represents a single user's session. * @View@. The presentation manager, used to render pages to the user. * @Application@. The controller that ties it all together. (Of course, a _real_ online forum application would be significantly more complex, but the above components will do for our purposes.) The dependencies between these components are: * @Authenticator@ _has_ @Database@ (for querying user authentication information) and @Logger@ * @Database@ _has_ @Logger@ (for indicating database accesses and query times) * @Session@ _has_ @Database@ (for storing session information) and @Logger@ * @Application@ _has_ @Database@, @View@, @Session@, and @Authenticator@, and @Logger@
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5 entries across 5 versions & 1 rubygems