Added ref to FileWidget. (rjsf-team#355)

Author: dehli

README.md

@@ -378,6 +378,12 @@ const schema = {
 
 > Note that storing large dataURIs into form state might slow rendering.
 
+##### File widget input ref
+
+The included `FileWidget` exposes a reference to the `<input type="file" />` element node as an `inputRef` component property.
+
+This allows you to programmatically trigger the browser's file selector which can be used in a custom file widget.
+
 ### Object fields ordering
 
 The `uiSchema` object spec also allows you to define in which order a given object field properties should be rendered using the `ui:order` property:

src/components/widgets/FileWidget.js

@@ -100,6 +100,7 @@ class FileWidget extends Component {
  <div>
  <p>
  <input
+ ref={ref => this.inputRef = ref}
  id={id}
  type="file"
  disabled={readonly || disabled}