new multimethod template conventions

gistfile1.clj

(def account-columns
  "Columns for the account model. Will be used to specify
   the content of the generated table header cells."
  [{:name :select-all
    :content "Select All"}]

(defmulti th 
  "Multimethod template function. Dispatches on the value specified.
   If the value is a keyword and the first argument to the function when called is a map, 
   it looks up the value in the map for itself. E.g. given {:name :select-all}, calling
   (:name {:name :select-all}) returns :select-all, which is the value the multimethod is
   dispatched on."
  :name)

(defmethod th 
  "Template for the select all cell. node is a function which returns
   a DOM Element for the given markup."
  :select-all
  [column]
  (node [:th {:id (:name column)} (:content column)]))

(defmethod th
  "Default method implementation for table header cells."
  :default
  [column]
  (node [:th (:content column)]))

(deftemplate thead
  "Write your parent template code once. If you know that the children
   of this template may have many differnt templates, implement it as a multimethod!
   That way every new cell you have to design can simply be defined as above, without
   having to redefine or even touch this function again. Extensibility made simple."
  [columns]
  [:thead 
    [:tr 
      (for [column columns]
        (th column)))

(comment
  (thead account-columns) => 
  <thead>
    <tr>
      <th id=":select-all">"Select All"</th>
    </tr>
  </thead>
  "So why multimethods? Because the alternative is writing code like this: "
  (deftemplate th
    [column]
    (if (= (:name column) :select-all)
      (node [:th {:id (:name column)} (:content column)])
      ...
      (if...
        (if...
          (if...))
  "Which means this function will scale linearly with the number of different cell designs you want to make!
   But the real problem is that in order to make a change, update this function, or add a new template 
   you have to understand the entirety of this function. This is a trivial example, but in production I'm sure you've seen
   large, convoluted if/elses, switch statements, and their related irk that are confusing. With multimethods you can just
   write a new function and you're done!"
  )