Not as curious as me! Naval gazing is happening right now :). I realised this is part of a bigger question: https://groups.google.com/d/msg/clojure/C3mYu9fMXec/gGUF5rhhZfwJ
On 25 February 2015 at 13:19, Jeroen van Dijk <[email protected]> wrote: > Sounds reasonable. Though destructuring a component (I was guessing "db" etc > were fields of this particular component) isn't the same as passing the > whole system. I'm guessing that you have a lot bigger system in mind than > these few commands. I don't have experience with that approach. I'm curious > to see what you'll end up with. > > Cheers, > Jeroen > > On Wed, Feb 25, 2015 at 2:01 PM, Colin Yates <[email protected]> wrote: >> >> Yes, I did consider that but didn't like the idea of passing the >> system around. Also handle-command would need access to the system as >> well. >> >> I am wondering whether simply having a 'registry' component which >> handlers register themselves with (e.g. a map of {predicate handler}) >> isn't a way forward and not using defmulti... >> >> On 25 February 2015 at 12:51, Jeroen van Dijk >> <[email protected]> wrote: >> > So I guess another question is where "handle-command" is being called. >> > What >> > about providing the component as argument to the multimethod (there are >> > other approaches too depending on your need). So: >> > >> > (defmulti handle-command(fn [component command] (first command))) >> > >> > (defmethod handle-command :add-customer [{:keys [db eventstore} [[_ >> > customer]]] >> > ... ) >> > >> > Isn't something like this enough? >> > >> > Jeroen >> > >> > On Wed, Feb 25, 2015 at 1:34 PM, Colin Yates <[email protected]> >> > wrote: >> >> >> >> Hi Jeroen - sure. >> >> >> >> I have a gateway which can handle a number of 'commands', let's say: >> >> >> >> AddCustomerCommand >> >> ExportQueryCommand >> >> >> >> to handle the AddCustomerCommand I need access to a database and an >> >> eventstore. To handle ExportQueryCommand I need access to the >> >> database, a PDF service and so on. >> >> >> >> One way of achieving this is (assuming commands are of the form >> >> [:command-discriminator payload]: >> >> >> >> (defmulti handle-command first) >> >> >> >> (defn add-customer [db eventstore customer] >> >> ...) >> >> >> >> (defrecord AddCustomerComponent [db eventstore] >> >> ... >> >> (start [this] (defmethod handle-command :add-customer [[_ customer]] >> >> (add-customer db eventstore customer))..) >> >> >> >> (defn export-reports [db pdf-generator] >> >> ...) >> >> >> >> (defrecord ExportQueryCommand [db pdf-generator] >> >> ... >> >> (start [this] (defmethod handle-command :export-query [[_]] >> >> (export-query db pdf-generator))..) >> >> >> >> and so on. >> >> >> >> Fundamentally my question is one of dispatching where the target of >> >> the dispatch requires collaborators that aren't part of the dispatch >> >> payload. >> >> >> >> Does that clarify? >> >> >> >> On 25 February 2015 at 12:11, Jeroen van Dijk >> >> <[email protected]> wrote: >> >> > I would try to stay away from any nested def's in components (but >> >> > also >> >> > in >> >> > other functions). I'm using component a lot and I never had the need >> >> > for >> >> > this. >> >> > >> >> > Maybe you can elaborate on why you think you need a multimethod >> >> > inside >> >> > the >> >> > component? Maybe a full example? >> >> > >> >> > Cheers, >> >> > Jeroen >> >> > >> >> > >> >> > >> >> > On Wed, Feb 25, 2015 at 12:08 PM, Colin Yates <[email protected]> >> >> > wrote: >> >> >> >> >> >> Hi, >> >> >> >> >> >> I have a number of commands flying around which need to be handled. >> >> >> defmulti/defmethod seem a nice answer. The problem is that each >> >> >> command >> >> >> handler will need different collaborators (those with long memories >> >> >> will >> >> >> realise this isn't new ground here ;)). >> >> >> >> >> >> I want to do something like: >> >> >> >> >> >> (ns one) >> >> >> (defmulti handle first) >> >> >> >> >> >> (ns two) >> >> >> (defrecord CommandAHandler [collab-1 collab-2] >> >> >> component/Lifecycle >> >> >> (start [this] >> >> >> (defmethod handle :command-a .... >> >> >> (collab-1 ...))) >> >> >> >> >> >> I realise that the lifecycle of defmethod doesn't match the >> >> >> component >> >> >> (i.e. stopping can't unregister the defmethod), but my main >> >> >> reservation >> >> >> is >> >> >> that a nested defmethod feels a bit weird. Has anyone done anything >> >> >> like >> >> >> this before? >> >> >> >> >> >> Thanks! >> >> >> >> >> >> -- >> >> >> You received this message because you are subscribed to the Google >> >> >> Groups "Clojure" group. >> >> >> To post to this group, send email to [email protected] >> >> >> Note that posts from new members are moderated - please be patient >> >> >> with >> >> >> your first post. >> >> >> To unsubscribe from this group, send email to >> >> >> [email protected] >> >> >> 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 [email protected]. >> >> >> For more options, visit https://groups.google.com/d/optout. >> >> > >> >> > >> >> > -- >> >> > You received this message because you are subscribed to the Google >> >> > Groups "Clojure" group. >> >> > To post to this group, send email to [email protected] >> >> > Note that posts from new members are moderated - please be patient >> >> > with >> >> > your >> >> > first post. >> >> > To unsubscribe from this group, send email to >> >> > [email protected] >> >> > 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 [email protected]. >> >> > For more options, visit https://groups.google.com/d/optout. >> >> >> >> -- >> >> You received this message because you are subscribed to the Google >> >> Groups "Clojure" group. >> >> To post to this group, send email to [email protected] >> >> Note that posts from new members are moderated - please be patient with >> >> your first post. >> >> To unsubscribe from this group, send email to >> >> [email protected] >> >> 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 [email protected]. >> >> For more options, visit https://groups.google.com/d/optout. >> > >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups "Clojure" group. >> > To post to this group, send email to [email protected] >> > Note that posts from new members are moderated - please be patient with >> > your >> > first post. >> > To unsubscribe from this group, send email to >> > [email protected] >> > 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 [email protected]. >> > For more options, visit https://groups.google.com/d/optout. >> >> -- >> You received this message because you are subscribed to the Google >> Groups "Clojure" group. >> To post to this group, send email to [email protected] >> Note that posts from new members are moderated - please be patient with >> your first post. >> To unsubscribe from this group, send email to >> [email protected] >> 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 [email protected]. >> For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to [email protected] > Note that posts from new members are moderated - please be patient with your > first post. > To unsubscribe from this group, send email to > [email protected] > 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 [email protected]. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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