diff --git a/src/re_frame/std_interceptors.cljc b/src/re_frame/std_interceptors.cljc index b47df97..9e546fa 100644 --- a/src/re_frame/std_interceptors.cljc +++ b/src/re_frame/std_interceptors.cljc @@ -14,7 +14,9 @@ "An interceptor which logs data about the handling of an event. Includes a `clojure.data/diff` of the db, before vs after, showing - the changes caused by the event handler. + the changes caused by the event handler. You absolutely will have + to understand https://clojuredocs.org/clojure.data/diff to + understand the output. You'd typically want this interceptor after (to the right of) any path interceptor. @@ -23,14 +25,14 @@ can be slow. So, you won't want this interceptor present in production code. So condition it out like this: - (re-frame.core/reg-event + (re-frame.core/reg-event-db :evt-id [(when ^boolean goog.DEBUG re-frame.core/debug)] ;; <-- conditional (fn [db v] ...)) - You'll also have to set goog.DEBUG to false in your production builds - look - in project.clj of /examples/todomvc. + To make this code fragment work, you'll also have to set goog.DEBUG to + false in your production builds - look in `project.clj` of /examples/todomvc. " (->interceptor :id :debug @@ -58,7 +60,7 @@ (def trim-v "An interceptor which removes the first element of the event vector, - allowing you to write more aesthetically pleasing db handlers. No + allowing you to write more aesthetically pleasing event handlers. No leading underscore on the event-v! Your event handlers will look like this: @@ -145,18 +147,28 @@ (defn path - "An interceptor factory which supplies a sub-path of `:db` to the handler. - It's action is somewhat analogous to clojure's `update-in`. It grafts the return - value from the handler back into db. + "An interceptor factory which supplies the value at a sub-path of `db` to + the handler, rather than all of `db`. + Afterwards, it grafts the handler's return value back into db, at the right path. + Its overall action is to make the handler behave like the function you + might give to clojure's `update-in`. - Usage: + Examples: (path :some :path) (path [:some :path]) (path [:some :path] :to :here) (path [:some :path] [:to] :here) + Example Use: + + (reg-event-db + :event-id + (path [:a :b]) ;; used here, in interceptor chain + (fn [b v] ;; 1st arg is now not db. Is the value from that path within db + ... new-b)) ;; must return a new value for that path (not db) + Notes: - 1. `path` may appear more than once in an interceptor chain + 1. `path` may appear more than once in an interceptor chain. Progressive narrowing. 2. if `:effects` contains no `:db` effect, can't graft a value back in. " [& args] @@ -249,13 +261,13 @@ "Interceptor factory which runs a given function `f` in the \"after\" position, presumably for side effects. - `f` is called with two arguments: the `effects` value of `:db` + `f` is called with two arguments: the `:effects` value for `:db` (or the `coeffect` value of db if no db effect is returned) and the event. - Its return value is ignored so `f` can only side-effect. + Its return value is ignored, so `f` can only side-effect. Examples use can be seen in the /examples/todomvc: - `f` runs schema validation (reporting any errors found). - - `f` writes some aspect of db to localstorage." + - `f` writes to localstorage." [f] (->interceptor :id :after