Provide a cursor into a Reagent atom. Behaves like a Reagent atom but focuses updates and derefs to the specified path within the wrapped Reagent atom. e.g., (let [c (cursor ra [:nested :content])] ... @c ;; equivalent to (get-in @ra [:nested :content]) ... (reset! c 42) ;; equivalent to (swap! ra assoc-in [:nested :content] 42) ... (swap! c inc) ;; equivalence to (swap! ra update-in [:nested :content] inc) ) The first parameter can also be a function, that should look something like this: (defn set-get ([k] (get-in @state k)) ([k v] (swap! state assoc-in k v))) The function will be called with one argument – the path passed to cursor – when the cursor is deref'ed, and two arguments (path and new value) when the cursor is modified. Given that set-get function, (and that state is a Reagent atom, or another cursor) these cursors are equivalent: (cursor state [:foo]) and (cursor set-get [:foo]). Note that a cursor is lazy: its value will not change until it is used. This may be noticed with add-watch.