clojure - Why is the ^ character used in this ClojureScript snippet? -

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in clojurescript re-frame todomvc application find following snippet in todomvc.views namespace.

(defn todo-list   [visible-todos]   [:ul.todo-list    (for [todo  @visible-todos]      ^{:key (:id todo)} [todo-item todo])])

although have read clojure chapter on metadata don't quite understand purpose of:

^{:key

in snippet above. please explain.

the :key react needs when have many items, can unique within group. latest version of react not need these keys. if use latest versions of reframe / reagent, try without :key metadata.

this metadata equivalent placing :key within component. example have equivalent to: 

[todo-item {:key (:id todo)} todo]

using metadata approach convenience, must in cases easier 'first key in props passed component' approach.

here's more explanation.


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