Using React Native MapView in ClojureScript Reagent - react-native

Question

I am trying to use MapView from https://github.com/airbnb/react-native-maps using Reagent. It works fine but how could I get local state for MapView when onRegionChange event is fired? Trying to use current/component but it is always nil.
(def Expo (js/require "expo"))
(def map-view (r/adapt-react-class (.-MapView Expo)))
(defn my-map []
(r/create-class
{:component-did-mount (fn [this]
(println "component mount "))
:reagent-render (fn []
(let [this (r/current-component)]
[map-view {:style {:flex 1}
:initialRegion {:latitude 37.78825
:longitude -122.4324
:latitudeDelta 0.0922
:longitudeDelta 0.0421}
:onRegionChange (fn []
;; Would like to see state here.
(println (.. this -state)) )}]))}))

Answer 1

Region information
The onRegionChange callback has Region as argument. Region has the following signature:
type Region {
latitude: Number,
longitude: Number,
latitudeDelta: Number,
longitudeDelta: Number,
}
You can get the values from the Region by using goog.object/get.
If you get the region and extract the values from it your my-map looks like:
(defn my-map []
[map-view {:style {:flex 1}
:initialRegion {:latitude 52.3702
:longitude 4.89516
:latitudeDelta 0.0922
:longitudeDelta 0.0421}
:onRegionChange (fn [region]
(alert (str "Latitude: "
(goog.object/get region "latitude")
"\nLongitude: "
(goog.object/get region "longitude"))))}])
You can obtain the latitudeDelta and longitudeDelta in the same manner.
When you drag the map the latitude and longitude show up:
The component
If you want access to the component itself your code works fine, you just have to visualize it:
(defn jsx->clj
[x]
(into {} (for [k (.keys js/Object x)] [k (aget x k)])))
(defn my-map []
(let [this (r/current-component)]
[map-view {:style {:flex 1}
:initialRegion {:latitude 37.78825
:longitude -122.4324
:latitudeDelta 0.0922
:longitudeDelta 0.0421}
:onRegionChange (fn [region]
;; Would like to see state here.
(alert "The component..."
(str (jsx->clj this))))}]))
This prints something like:
Not sure if you can do anything with the component, I think you need the Region information.