DRY up photo & model interaction

* move stuff in models into a concern
 * create combined collection for all models that have photos

app/models/concerns/photo_capable.rb

@@ -0,0 +1,18 @@
+module PhotoCapable
+  extend ActiveSupport::Concern
+
+  included do
+    has_and_belongs_to_many :photos
+
+    before_destroy :remove_from_list
+  end
+
+  def remove_from_list
+    photolist = self.photos.to_a # save a temp copy of the photo list
+    self.photos.clear # clear relationship b/w object and photo
+
+    photolist.each do |photo|
+      photo.destroy_if_unused
+    end
+  end
+end

app/models/garden.rb

@@ -1,23 +1,13 @@
 class Garden < ActiveRecord::Base
-  include Geocodable
   extend FriendlyId
+  include Geocodable
+  include PhotoCapable
   friendly_id :garden_slug, use: [:slugged, :finders]
 
   belongs_to :owner, class_name: 'Member', foreign_key: 'owner_id'
   has_many :plantings, -> { order(created_at: :desc) }, dependent: :destroy
   has_many :crops, through: :plantings
 
-  has_and_belongs_to_many :photos
-
-  before_destroy do |garden|
-    photolist = garden.photos.to_a # save a temp copy of the photo list
-    garden.photos.clear # clear relationship b/w garden and photo
-
-    photolist.each do |photo|
-      photo.destroy_if_unused
-    end
-  end
-
   # set up geocoding
   geocoded_by :location
   after_validation :geocode

app/models/harvest.rb

@@ -1,22 +1,13 @@
 class Harvest < ActiveRecord::Base
-  include ActionView::Helpers::NumberHelper
   extend FriendlyId
+  include ActionView::Helpers::NumberHelper
+  include PhotoCapable
   friendly_id :harvest_slug, use: [:slugged, :finders]
 
   belongs_to :crop
   belongs_to :owner, class_name: 'Member'
   belongs_to :plant_part
 
-  has_and_belongs_to_many :photos
-
-  before_destroy do |harvest|
-    photolist = harvest.photos.to_a # save a temp copy of the photo list
-    harvest.photos.clear # clear relationship b/w harvest and photo
-
-    photolist.each do |photo|
-      photo.destroy_if_unused
-    end
-  end
 
   default_scope { order('created_at DESC') }
 

app/models/photo.rb

@@ -1,22 +1,26 @@
 class Photo < ActiveRecord::Base
+  ON_MODELS = %w(plantings harvests gardens)
   belongs_to :owner, class_name: 'Member'
 
-  has_and_belongs_to_many :plantings
-  has_and_belongs_to_many :harvests
-  has_and_belongs_to_many :gardens
-  before_destroy do |photo|
-    photo.plantings.clear
-    photo.harvests.clear
-    photo.gardens.clear
+  ON_MODELS.each do |relation|
+    has_and_belongs_to_many relation.to_sym
   end
 
+  before_destroy { relationships.clear }
+
   default_scope { order("created_at desc") }
 
+  def relationships
+    associations = []
+    ON_MODELS.each do |association_name, _reflection|
+      associations << self.send("#{association_name}").to_a
+    end
+    associations.flatten!
+  end
+
   # remove photos that aren't used by anything
   def destroy_if_unused
-    unless plantings.size > 0 or harvests.size > 0 or gardens.size > 0
-      self.destroy
-    end
+    self.destroy unless relationships.size > 0
   end
 
   # This is split into a side-effect free method and a side-effecting method

app/models/planting.rb

@@ -1,22 +1,12 @@
 class Planting < ActiveRecord::Base
   extend FriendlyId
+  include PhotoCapable
   friendly_id :planting_slug, use: [:slugged, :finders]
 
   belongs_to :garden
   belongs_to :owner, class_name: 'Member', counter_cache: true
   belongs_to :crop, counter_cache: true
 
-  has_and_belongs_to_many :photos
-
-  before_destroy do |planting|
-    photolist = planting.photos.to_a # save a temp copy of the photo list
-    planting.photos.clear # clear relationship b/w planting and photo
-
-    photolist.each do |photo|
-      photo.destroy_if_unused
-    end
-  end
-
   default_scope { order("created_at desc") }
   scope :finished, -> { where(finished: true) }
   scope :current, -> { where(finished: false) }

spec/models/photo_spec.rb

@@ -85,11 +85,13 @@ describe Photo do
 
         planting.destroy # photo is still used by harvest and garden
         photo.reload
+
         expect(photo.plantings.size).to eq 0
         expect(photo.harvests.size).to eq 1
 
         harvest.destroy
         garden.destroy # photo is now no longer used by anything
+        photo.reload
 
         expect(photo.plantings.size).to eq 0
         expect(photo.harvests.size).to eq 0