Added count method for associations (#392)

* Added count method for associations

only for has_many

* test for through count

* Update associations_spec.cr

spec/associations_spec.cr

@@ -47,6 +47,15 @@ describe Avram::Model do
 
       post.tags.should eq [tag]
     end
+
+    it "count through associations" do
+      tag = TagBox.create
+      post = PostBox.create
+      TagBox.create
+      TaggingBox.new.tag_id(tag.id).post_id(post.id).create
+
+      post.tags_count.should eq 1
+    end
   end
 
   describe "has_one" do
@@ -103,6 +112,13 @@ describe Avram::Model do
 
         LineItemQuery.new.find(item.id).scans.should eq [scan]
       end
+
+      it "gets amount of records" do
+        item = LineItemBox.create
+        ScanBox.new.line_item_id(item.id).create
+
+        item.scans_count.should eq 1
+      end
     end
 
     describe "has_many through a join table" do

src/avram/associations/has_many.cr

@@ -83,6 +83,24 @@ module Avram::Associations::HasMany
       @_preloaded_{{ assoc_name }} || lazy_load_{{ assoc_name }}
     end
 
+    def {{ assoc_name.id }}_count : Int64
+      {% if through %}
+        {{ model }}::BaseQuery
+          .new
+          .join_{{ through.id }}
+          .__yield_where_{{ through.id }} do |through_query|
+            through_query.{{ foreign_key.id }}(id)
+          end
+          .preload_{{ through.id }}
+          .select_count
+      {% else %}
+        {{ model }}::BaseQuery
+          .new
+          .{{ foreign_key }}(id)
+          .select_count
+      {% end %}
+    end
+
     private def maybe_lazy_load_{{ assoc_name }}  : Array({{ model }})?
       if lazy_load_enabled?
         lazy_load_{{ assoc_name }}