How to access current_user in partial of public_activity gem?

When I m trying to access current_user in partial file it will contains nil value.

I used devise gem for login process. I also used public_activity gem for generating notification.

I have notification controller as below.

def index
    @activities = PublicActivity::Activity.all      
end

In views/notifications/index.html.erb

<%= render @activities %>

Now in views/public_activity/commontator_comment/_create.html.erb

in this partial I want to access current_user but it contains nil value.

I didn't understand what was the problem.

please help me. thanks in advance.