How to get ref of DataTable

[bluu926]

Using the latest primereact: 1.6.2

I was trying to exportCSV() following this:
http://primefaces.org/primereact/#/datatable/export

I'm using the following in <DataTable>

ref={(el) => { this.dt = el; }

Then I have a Button that does an onlock for:

this.dt

However, I get a undefined error for dt.