Implemented support for the SUM aggregate function

CHANGELOG.md

@@ -2,14 +2,14 @@
 
 ## Not released
 
+## 0.10.1
+* Added support for 'or' and 'not' clauses (https://github.com/Beyond-Finance/active_force/pull/13)
+* Added support for the SUM aggregate function (https://github.com/Beyond-Finance/active_force/pull/14)
 ## 0.10.0
 * Fix `#where` chaining on `ActiveQuery` (https://github.com/Beyond-Finance/active_force/pull/7)
 * Add `#find_by!` which raises `ActiveForce::RecordNotFound` if nothing is found. (https://github.com/Beyond-Finance/active_force/pull/8)
 * Fix `#includes` to find, build, and set the association. (https://github.com/Beyond-Finance/active_force/pull/12)
 
-## 0.10.1
-* Added support for 'or' and 'not' clauses (https://github.com/Beyond-Finance/active_force/pull/13)
-
 ## 0.9.1
 * Fix invalid error class (https://github.com/Beyond-Finance/active_force/pull/6)
 

README.md

@@ -185,6 +185,16 @@ It is also possible to eager load associations:
 Comment.includes(:post)
 ```
 
+### Aggregates
+
+Summing the values of a column:
+```ruby
+Transaction.where(offer_id: 'ABD832024').sum(:amount)
+#=> This will query "SELECT SUM(Amount__c) 
+#                    FROM Transaction__c 
+#                    WHERE offer_id = 'ABD832024'"
+```
+
 #### Decorator
 
 You can specify a `self.decorate(records)` method on the class, which will be called once with

lib/active_force/active_query.rb

@@ -35,6 +35,11 @@ def count
       sfdc_client.query(to_s).first.expr0
     end
 
+    def sum field
+      super(mappings[field])
+      sfdc_client.query(to_s).first.expr0
+    end
+
     def limit limit
       super
       limit == 1 ? to_a.first : self

lib/active_force/query.rb

@@ -96,6 +96,11 @@ def count
       self
     end
 
+    def sum field
+      @query_fields = ["sum(#{field})"]
+      self
+    end
+
     protected
       def and_conditions
         "(#{@conditions.join(') AND (')})" unless @conditions.empty?

lib/active_force/sobject.rb

@@ -27,7 +27,7 @@ class SObject
 
     class << self
       extend Forwardable
-      def_delegators :query, :not, :or, :where, :first, :last, :all, :find, :find_by, :find_by!, :count, :includes, :limit, :order, :select, :none
+      def_delegators :query, :not, :or, :where, :first, :last, :all, :find, :find_by, :find_by!, :sum, :count, :includes, :limit, :order, :select, :none
       def_delegators :mapping, :table, :table_name, :custom_table?, :mappings
 
       private

spec/active_force/query_spec.rb

@@ -139,4 +139,14 @@
       expect(query.where("name = 'cool'").count.to_s).to eq "SELECT count(Id) FROM table_name WHERE (name = 'cool')"
     end
   end
+
+  describe ".sum" do
+    it "should return the query for summing the desired column" do
+      expect(query.sum(:field1).to_s).to eq 'SELECT sum(field1) FROM table_name'
+    end
+
+    it "should work with a condition" do
+      expect(query.where("name = 'cool'").sum(:field1).to_s).to eq "SELECT sum(field1) FROM table_name WHERE (name = 'cool')"
+    end
+  end
 end