Expose root ref by default to allow automatic forwarding of setNativeProps

[bitmage]

In React Native, TouchableHighlight requires its children to forward 'setNativeProps'. This is implemented in built-in components, but must be manually implemented for all custom components.

This causes big incompatibilities with a library like Native Base, not to mention any custom components that the developer creates, which is apparently a preferred pattern for theming:

For our projects, we create a common directory inside the main js directory. This folder houses commonly-reused components throughout the app. For example, we can declare common Text and Header components...

It could be remedied by making available a default ref root which points to the root node. This would allow generic forwarding to be written into a base class, which other components could inherit from:

setNativeProps(props) {
  this.refs.root.setNativeProps(props)
}

This would essentially forward the props down the chain until we hit a "concrete" built-in component. Any arguments against making a root ref available by default?

[gaearon]

Yes, refs are not free, and making them always available is going to hurt performance and memory usage.

Maybe in the future this could be solved by #4213.