How to find index of records rendered by a partial with collection in Rails

Using render partial with collection how to find the index of the records?

Somewhere I found that someone is commented like,
“It seems this is an undocumented feature of rails.”

Anyway we can find this by using ‘recordName_counter’.

Render a partial with collection

= render :partial = > "person", :collection => @winners
Name: = person.name 

In Partial write

  Rank: = person_counter + 1
  Name: = person.name 

Result

Rank: 1 Name: Peter
Rank: 2 Name: Paul
Rank: 3 Name: Mary