The very final step is to create the JavaScript module that defines the interface layer between Java and JavaScript for the users of your new view. Much of the effort is handled by internal React code in Java and JavaScript and all that is left for you is to describe the propTypes.
requireNativeComponent commonly takes two parameters, the first is the name of the native view and the second is an object that describes the component interface. The component interface should declare a friendly name for use in debug messages and must declare the propTypes reflected by the Native View. The propTypes are used for checking the validity of a user's use of the native view. Note that if you need your JavaScript component to do more than just specify a name and propTypes, like do custom event handling, you can wrap the native component in a normal react component. In that case, you want to pass in the wrapper component instead of iface to requireNativeComponent. This is illustrated in the MyCustomView example below.
So now we know how to expose native view components that we can control easily from JS, but how do we deal with events from the user, like pinch-zooms or panning? When a native event occurs the native code should issue an event to the JavaScript representation of the View, and the two views are linked with the value returned from the getId() method.