Further cleanup around fix for #78

examples/todomvc/src/todomvc/db.cljs

@@ -8,20 +8,20 @@
 ;; This is a Prismatic Schema which documents the structure of app-db
 ;; See: https://github.com/Prismatic/schema
 ;;
-;; The value in app-db should ALWAYS match this schema. The value in app-db
-;; can ONLY be changed by event handlers so, after each handler has run, we
-;; re-check that app-db still matches this schema.
+;; The value in app-db should ALWAYS match this schema. Now, the value in
+;; app-db can ONLY be changed by event handlers so, after each event handler
+;; has run, we re-check that app-db still matches this schema.
 ;;
 ;; How is this done? Look in handlers.cljs and you'll notice that all handers
-;; have an "after" middleware which does the re-check.
+;; have an "after" middleware which does the schema re-check.
 ;;
-;; None of this is strickly necessary. It could  be omitted. But we find it
+;; None of this is strictly necessary. It could  be omitted. But we find it
 ;; good practice.
 
 (def schema {;; a sorted-map is used to hold the todos.
              :todos    (s/both PersistentTreeMap        ;; ensure sorted-map, not just map
                                
-                               ;; each todos is keyed by its :id value
+                               ;; each todo is keyed by its integer :id value
                                {s/Int {:id s/Int :title s/Str :done s/Bool}})
 
              ;; controls what todos are shown/visible to the user
@@ -43,8 +43,8 @@
 
 ;; -- Local Storage  ----------------------------------------------------------
 ;;
-;; Part of the todomvc challenge is to ongoingly store the todos in LocalStorage.
-;; On app startup, must reload the todos from when the program was last run.
+;; Part of the todomvc challenge is to store the todos in LocalStorage, and
+;; on app startup, reload the todos from when the program was last run.
 ;; But not the setting for "showing" filter. Just the todos.
 ;;
 

examples/todomvc/src/todomvc/handlers.cljs

@@ -8,21 +8,21 @@
 ;; -- Middleware --------------------------------------------------------------
 ;;
 
-(defn schema-checker
-      "throw error with schema details if schema does not match.
-      For better errors, tag your schema with :ref metadata
-      e.g. (def my-schema ^{:ref (ns-line)} {...my schema....}"
-      [db]
-      (if-let [problems  (s/check schema db)]
-          (throw (js/Error. (str "schema check failed: " problems)))))
+(defn check-and-throw
+      "throw an exception if db doesn't match the schema."
+      [a-schema db]
+      (if-let [problems  (s/check a-schema db)]
+         (throw (js/Error. (str "schema check failed: " problems)))))
 
-(def check-schema (after schema-checker))
+;; after an event handler has run, this middleware can check that
+;; it the value in app-db still correctly matches the schema.
+(def check-schema-mw (after (partial check-and-throw schema)))
 
 
 (def ->ls (after todos->ls!))    ;; middleware to store todos into local storage
 
 ;; middleware for any handler that manipulates todos
-(def todo-middleware [check-schema    ;; after ever event handler make sure the schema is still valid
+(def todo-middleware [check-schema-mw ;; after ever event handler make sure the schema is still valid
                       (path :todos)   ;; 1st param to handler will be value from this path
                       ->ls            ;; write to localstore each time
                       trim-v])        ;; remove event id from event vec
@@ -43,14 +43,14 @@
                                   ;; usage:  (dispatch [:initialise-db])
 (register-handler                 ;; On app startup, ceate initial state
   :initialise-db                  ;; event id being handled
-  check-schema
+  check-schema-mw
   (fn [_ _]                       ;; the handler being registered
     (merge default-value (ls->todos))))  ;; all hail the new state
 
 
 (register-handler                 ;; this handler changes the footer filter
   :set-showing                    ;; event-id
-  [check-schema (path :showing) trim-v]        ;; middleware  (wraps the handler)
+  [check-schema-mw (path :showing) trim-v]  ;; middleware  (wraps the handler)
 
   ;; Because of the path middleware above, the 1st parameter to
   ;; the handler below won't be the entire 'db', and instead will