Reagent component doesn't update

Question

The 'add' and 'remove' items of shoppinglist ratom updates the 'shopping-list' component, but the 'update' doesn't.

I used cljs REPL for updating the shoppinglist ratom.

add:

shopping.app=> (swap! shoppinglist assoc 3 {:id 3, :name "Coke", :price 25})
WARNING: Use of undeclared Var shopping.app/shoppinglist at line 1 <cljs repl>
{1 {:id 1, :name "Bread", :price 23}, 2 {:id 2, :name "Milk", :price 12}, 3 {:id 3, :name "Coke", :price 25}}

remove:

shopping.app=> (swap! shoppinglist dissoc 3)
WARNING: Use of undeclared Var shopping.app/shoppinglist at line 1 <cljs repl>
{1 {:id 1, :name "Bread", :price 20}, 2 {:id 2, :name "Milk", :price 12}}

update:

shopping.app=> (swap! shoppinglist assoc 2 {:id 2, :name "Milk", :price 8})
WARNING: Use of undeclared Var shopping.app/shoppinglist at line 1 <cljs repl>
{1 {:id 1, :name "Bread", :price 20}, 2 {:id 2, :name "Milk", **:price 8**}}
shopping.app=>

The shoppinglist ratom is updated, I checked it in the REPL, but the component is not updated.

(ns shopping.app
  (:require [reagent.core :as r]))

(defonce shoppinglist (r/atom (sorted-map
                           1 {:id 1 :name "Bread" :price 20},
                           2 {:id 2 :name "Milk" :price 12})))

(defn shopping-item [item]
  (let [{:keys [id name price]} item]
    (fn []
      [:div
        [:label id]
        [:label (str " | " name)]
        [:label (str " | " price)]])))

(defn shopping-list []
  [:div.container
    (for [item (vals @shoppinglist)]
      ^{:key (:id item)} [:div
        [shopping-item item]])])

(defn init
  "Initialize components."
  []
  (let [container (.getElementById js/document "container")]
    (r/render-component 
      [shopping-list] 
      container)))

EDITED ==================================

I found a good overview about the component designs here https://github.com/reagent-project/reagent/blob/master/docs/CreatingReagentComponents.md

Form-2: I didn't put the local state into my example, but my real app contains local stater ratom. According this, I had to put the same parameters for the embedded render functions what the component function has. I modified my example, added local state ratom and params the render function and it works well.

(ns shopping.app
  (:require [reagent.core :as r]))

(defonce shoppinglist (r/atom (sorted-map
                           1 {:id 1 :name "Bread" :price 20},
                           2 {:id 2 :name "Milk" :price 12})))

(defn shopping-item [{:keys [id name price]}]
  (let [loacalstate (r/atom true)]
    (fn [{:keys [id name price]}]
      [:div
        [:label id]
        [:label (str " | " name)]
        [:label (str " | " price)]])))

(defn shopping-list []
  [:div.container
    (for [item (vals @shoppinglist)]
      ^{:key (:id item)} [:div
        [shopping-item item]])])

(defn init
  "Initialize components."
  []
  (let [container (.getElementById js/document "container")]
    (r/render-component 
      [shopping-list] 
      container)))

Answer 1

Remove the inner no-arg wrapping function in shopping-item. It is unnecessary, but will prevent re-rendering of existing items, because the no-arg function doesn't see the changed argument.

So:

(defn shopping-item [item]
  (let [{:keys [id name price]} item]
    [:div
     [:label id]
     [:label (str " | " name)]
     [:label (str " | " price)]]))

or

(defn shopping-item [{:keys [id name price]}]
  [:div
   [:label id]
   [:label (str " | " name)]
   [:label (str " | " price)]])

For more information, check out this documentation of form-2 components:

https://github.com/reagent-project/reagent/blob/master/doc/CreatingReagentComponents.md#form-2--a-function-returning-a-function