ruby - How to sort an array of class objects based on date? -

i have following array of hashes:

@products = {#<productproxy:0xb486d148 @pa={"productavailabledatets"=>"2013-12-04t23:07:12.592z", "mprice"=>, "pstock"=>, "id"=>, "productid"=>, "productdesignerid"=>}>, #<productproxy:0xb4adf304 @pa={"productavailabledatets"=>"2013-1-04t23:07:12.592z", "mprice"=>, "pstock"=>, "id"=>, "productid"=>, "productdesignerid"=>}>, #<productproxy:0xb4adecec @pa={"productavailabledatets"=>"2013-15-03t23:07:12.592z", "mprice"=>, "pstock"=>, "id"=>, "productid"=>, "productdesignerid"=>}>,  ... } 

i want sort array based on productavailabledatets value, in descending order. tried doing following:

@products = @products.sort_by{ |k| -k['productavailabledatets'] }  

but doing so, not able access productavailabledatets field. tried print @products[0]['productavailabledatets']. prints nil. how can access field correctly?

if don't need data sorted database (assumed got data active record), can convert array , sort it:

@products.to_a.sort{ |a,b| b.productavailabledatets <=> a.productavailabledatets } 

if array:

@products.sort{ |a,b| b.productavailabledatets <=> a.productavailabledatets } 

edit: missed order. order implemented changing first , second parameter.