fix(ref): Handle ref objects in children prop.

Author: joaovieira

src/IntersectionObserver.js

@@ -104,9 +104,18 @@ export default class IntersectionObserver extends React.Component {
     };
 
     handleNode = target => {
-        if (typeof this.props.children.ref === 'function') {
-            this.props.children.ref(target);
+        /**
+         * Forward hijacked ref to user.
+         */
+        const nodeRef = this.props.children.ref;
+        if (nodeRef) {
+            if (typeof nodeRef === 'function') {
+                nodeRef(target);
+            } else if (typeof nodeRef === 'object') {
+                nodeRef.current = target;
+            }
         }
+
         /**
          * This is a bit ugly: would like to use getSnapshotBeforeUpdate(), but we do not want to depend on
          * react-lifecycles-compat to support React versions prior to 16.3 as this extra boolean gets the job done.

src/__tests__/IntersectionObserver.spec.js

@@ -72,6 +72,19 @@ test('should call ref callback of children', () => {
     expect(spy).toHaveBeenCalledWith(target);
 });
 
+test('should handle children ref of type RefObject', () => {
+    const ref = React.createRef();
+    const component = (
+        <IntersectionObserver onChange={noop}>
+            <span ref={ref} />
+        </IntersectionObserver>
+    );
+
+    renderer.create(component, { createNodeMock: () => target });
+
+    expect(ref.current).toEqual(target);
+});
+
 test('options getter returns propTypes `root`, `rootMargin` and `threshold`', () => {
     const options = { root: { nodeType: 1 }, rootMargin: '50% 0%', threshold: [0, 1] };
     const component = (