Fix and properly document/test count(column_name) usage. Closes #8999 [lifofifo]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7192 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Fix and properly document/test count(column_name) usage. Closes #8999 [lifofifo]
+
 * Remove deprecated count(conditions=nil, joins=nil) usage.  Closes #8993 [lifofifo]
 
 * Change belongs_to so that the foreign_key assumption is taken from the association name, not the class name.  Closes #8992 [hasmanyjosh]

activerecord/lib/active_record/calculations.rb

@@ -6,12 +6,13 @@ module ActiveRecord
     end
 
     module ClassMethods
-      # Count operates using two different approaches.
+      # Count operates using three different approaches.
       #
       # * Count all: By not passing any parameters to count, it will return a count of all the rows for the model.
+      # * Count using column : By passing a column name to count, it will return a count of all the rows for the model with supplied column present
       # * Count using options will find the row count matched by the options used.
       #
-      # The second approach, count using options, accepts an option hash as the only parameter. The options are:
+      # The third approach, count using options, accepts an option hash as the only parameter. The options are:
       #
       # * <tt>:conditions</tt>: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
       # * <tt>:joins</tt>: An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed).
@@ -28,6 +29,9 @@ module ActiveRecord
       # Examples for counting all:
       #   Person.count         # returns the total count of all people
       #
+      # Examples for counting by column:
+      #   Person.count(:age)  # returns the total count of all people whose age is present in database
+      #
       # Examples for count with options:
       #   Person.count(:conditions => "age > 26")
       #   Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job) # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN.
@@ -123,19 +127,21 @@ module ActiveRecord
         def construct_count_options_from_args(*args)
           options     = {}
           column_name = :all
-
+          
           # We need to handle
           #   count()
+          #   count(:column_name=:all)
           #   count(options={})
           #   count(column_name=:all, options={})
-          if args[0].is_a?(Hash)
-            options = args[0]
-          elsif args[1].is_a?(Hash)
+          case args.size
+          when 1
+            args[0].is_a?(Hash) ? options = args[0] : column_name = args[0]
+          when 2
             column_name, options = args
           else
-            raise ArgumentError, "Unexpected parameters passed to count(options={}): #{args.inspect}"
+            raise ArgumentError, "Unexpected parameters passed to count(): #{args.inspect}"
           end if args.size > 0
-
+          
           [column_name, options]
         end
 

activerecord/test/calculations_test.rb

@@ -227,12 +227,20 @@ class CalculationsTest < Test::Unit::TestCase
     assert_raises(ArgumentError) { Company.send(:validate_calculation_options, :sum,   :foo => :bar) }
     assert_raises(ArgumentError) { Company.send(:validate_calculation_options, :count, :foo => :bar) }
   end
-
+  
   def test_should_count_selected_field_with_include
     assert_equal 6, Account.count(:distinct => true, :include => :firm)
     assert_equal 4, Account.count(:distinct => true, :include => :firm, :select => :credit_limit)
   end
-
+  
+  def test_count_with_column_parameter
+    assert_equal 5, Account.count(:firm_id)
+  end
+  
+  def test_count_with_column_and_options_parameter
+    assert_equal 2, Account.count(:firm_id, :conditions => "credit_limit = 50")
+  end
+  
   def test_count_with_no_parameters_isnt_deprecated
     assert_not_deprecated { Account.count }
   end