用re-frame实现一个登录系统

(reg-db
  :user {:username ""
         :password ""
         :logged-in? false})

(reg-event-db
  :update-username
  (fn [db [_ new-username]]
    (assoc-in db [:user :username] new-username)))

(reg-event-db
  :update-password
  (fn [db [_ new-password]]
    (assoc-in db [:user :password] new-password)))

(reg-event-db
  :login
  (fn [db _]
    (if (and (= (:username @db) "admin")
             (= (:password @db) "password"))
      (assoc-in db [:user :logged-in?] true)
      db)))

(defn login-view [db]
  [:div
   [:input {:type "text"
            :value (:username @db)
            :on-change #(re-frame/dispatch [:update-username %])}]
   [:input {:type "password"
            :value (:password @db)
            :on-change #(re-frame/dispatch [:update-password %])}]
   [:button {:on-click #(re-frame/dispatch [:login])} "Login"]])

(defn app-view [db]
  [:div
   (if (:logged-in? (:user @db))
     [:p "Welcome, admin!"]
     [login-view db])])

(reg-fx
  :render
  (fn [_ [_ db]]
    (reagent/render [app-view db]
                    (.getElementById js/document "app"))))

(defn ^:export init []
  (re-frame/dispatch-sync [:update-username ""])
  (re-frame/dispatch-sync [:update-password ""])
  (re-frame/dispatch [:render]))