CI 3 - input class

Hi,

Apologies if this is repeated. The documentation says the input class is

initialized automatically by the system so there is no need to do it manually.

But this code

Code:

$email = $this->input->post('email');

is generating this error

Fatal error: Call to undefined function post() in /home/ubuntu/workspace/application/controllers/admin/Homepage.php on line 46

What am I doing wrong ?