You can do this using multimethods. defmulti and defmethod will allow you
to do everything you ask for apart from adding a doc-string to each
command. Have a look at:
http://clojuredocs.org/clojure_core/clojure.core/defmulti
On Thursday, May 29, 2014 3:05:56 AM UTC+2, Will Duquette wrote:
>
> If there's a better place to ask this kind of question, please point me in
> the right direction!
>
> I'm learning Clojure, and part of the project I'm making is a command
> language: the user can type commands at the application in something like a
> REPL, and have a dialog with the application. I want to dispatch to a
> function that carries out the command based on the first word of the
> command; the function then receives the remaining words in the command, and
> can do with them what it likes. So I'm going to need a map, something like
>
> { "dothis" #'commands/dothis, "dothat" #'commands/dothat ...}
>
> The question is, how best to build up that map? I'd like to define a
> command like this:
>
> (command "dothis"
> "Documentation string"
> [argv]
> ....)
>
> and have (command) define the function and add the entry to the map.
>
> I can think of all kinds of ways to do this. I could define
>
> (def command-map {})
>
> and then have (command) rebind it:
>
> ...
> (def command-map (assoc command-map name function))
>
> but I know that's frowned upon. I could make command-map contain an atom,
> and use (swap!) to update the atom, but really, the mapping isn't going to
> change at run-time. I could make (command) a macro, so that it's really
> updating command-map at the top-level, but that seems cheesy.
>
> Or, I could make (command) define the function as a public function in the
> 'commands namespace, which would be reserved for that purpose, and attach
> the command name, e.g., "dothis" to the function as metadata. Then I could
> build the map by querying the namespace using (ns-publics).
>
> Is there is a normal way to do this kind of thing?
>
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