Using selected option in rails select_tag

select_tag rails

year array -> ['2012','2011','2010','2009']
selected year -> 2010

<%= select_tag 'year_range', options_for_select(['2012','2011','2010','2009'],'2010') %>

which will always selects '2010'


If you are selecting an object 

if the form is -> f
collection is @ages 
selected index is always 3

<%= f.select :age, options_from_collection_for_select(@ages, "id", "age",'3') %>

resources 

http://stackoverflow.com/questions/7347039/rails-select-tag-selected-value

http://apidock.com/rails/ActionView/Helpers/FormOptionsHelper/options_from_collection_for_select

Thanks!