Converting a sql query to rails activerecord

I have a simple problem . I am not able to figure out the rails equivalent for this sql query:

select COUNT(description) from reports where user_id = current_user;

Actually I want to count the total no. of reports posted by a particular user when logged in his account and not the开发者_JS百科 all reports posted by all users. I am also not able to figure out that how should I pass the user_id of the current user logged in so that I can get the required result. Please Help.

Something like:

current_user.reports.count

In Rails 2

If you have defined has_many :reports in User model.

count = current_user.reports.first(:select => "COUNT(description) as count").count

If has_many is not defined in the model,

count = Report.first(:select => "COUNT(description) as count",
             :conditions => {:user_id => current_user.id}).count

But current_user.reports.select{ |report| report.description }.count is enough though it produces a different query. (Select * from reports where ..) and then take the count of the array.

But in Rails 3, it is quite easy.

If you have defined has_many :reports in User model.

count = current_user.reports.count(:description)

otherwise

count = Report.where(:user_id => current_user.id).count(:description)

Refer Rails guide for Rails 3 AR calculation queries.