Hi Korny, Components implementing protocols can provide different implementations. In the Database example, both the "real" component and the "stub" component would have to implement some common protocol that defines the "primitive" capabilities needed by the application.
Traditional update-in-place databases are hard to mock, but I sometimes stub a remote Datomic database with a local in-memory version. -S On Sun, Jan 5, 2014 at 1:23 PM, Korny Sietsma <ko...@sietsma.com> wrote: > Hi - I've been playing with this and I'm a little confused. > > I can understand how you use the library to pass around stateful > components, and to start/stop them and wire them up etc. > > But I'm not sure I see how it should be used for more general dependency > injection. > > I'll pick a concrete example - in the readme you have an ExampleComponent > which calls "(get-user database :admin)" > the "get-user" function then gets the connection from the Database > component - but it's still coupled to the particular implementation of > "execute-query": > > (defn get-user [database username] > (execute-query (:connection database) > "SELECT * FROM users WHERE username = ?" > username)) > > If you wanted to unit test this function, you could pass whatever database > connection thing you'd like - but you couldn't stub out the whole database, > as execute-query is still coupled to the implementation of your database. > More generally, anything that calls "get-user" will need to provide some > sort of working database, or mock/stub out the call to execute-query, or > the call to get-user itself. > > Is there something I'm missing? Is there some way you could/would do this > with the component library? Or is this not the point of the library? > > - Korny > > > > On 21 November 2013 02:01, Stuart Sierra <the.stuart.sie...@gmail.com>wrote: > >> This is a small library/framework I've been working on for a few months. >> >> https://github.com/stuartsierra/component >> >> I use this to manage runtime state in combination with my "reloaded" >> workflow using tools.namespace.[1] >> >> I've started using this on some personal and professional projects and it >> seems to be working fairly well. >> >> >> [1]: http://thinkrelevance.com/blog/2013/06/04/clojure-workflow-reloaded >> >> -- >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to clojure@googlegroups.com >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> clojure+unsubscr...@googlegroups.com >> For more options, visit this group at >> http://groups.google.com/group/clojure?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "Clojure" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to clojure+unsubscr...@googlegroups.com. >> >> For more options, visit https://groups.google.com/groups/opt_out. >> > > > > -- > Kornelis Sietsma korny at my surname dot com http://korny.info > .fnord { display: none !important; } > > -- > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with > your first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en > --- > You received this message because you are subscribed to a topic in the > Google Groups "Clojure" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/clojure/jXnxVZaP2K4/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
