Cache interesting seeds fragment for homepage.

(refresh cache if any of them are deleted)

app/controllers/seeds_controller.rb

@@ -1,5 +1,8 @@
 class SeedsController < ApplicationController
   load_and_authorize_resource
+
+  cache_sweeper :seed_sweeper
+
   # GET /seeds
   # GET /seeds.json
   def index

app/models/seed.rb

@@ -30,21 +30,28 @@ class Seed < ActiveRecord::Base
     end
   end
 
+  def interesting?
+    # assuming we're passed something that's already known to be tradable
+    # eg. from Seed.tradable scope
+    return false if s.owner.location.blank? # don't want unspecified locations
+    return true
+  end
+
   # Seed.interesting
   # returns a list of interesting seeds, for use on the homepage etc
   def Seed.interesting
     howmany = 12 # max number to find
+    interesting_seeds = Array.new
 
-    return Rails.cache.fetch('interesting_seeds', :expires_in => 6.hours) do
-      interesting_seeds = Array.new
-      Seed.tradable.each do |s|
-        break if interesting_seeds.length == howmany
-        next if s.owner.location.blank? # don't want unspecified locations
+    Seed.tradable.each do |s|
+      break if interesting_seeds.length == howmany
+      if s.interesting?
         interesting_seeds.push(s)
       end
-      interesting_seeds
     end
 
+    return interesting_seeds
+
   end
 
   def seed_slug

app/models/seed_sweeper.rb

@@ -0,0 +1,12 @@
+class SeedSweeper < ActionController::Caching::Sweeper
+  observe Seed
+
+  def after_destroy(seed)
+    if seed.tradable? && seed.interesting?
+      Rails.cache.delete('interesting_seeds')
+    end
+  end
+
+end
+
+

app/views/home/_seeds.html.haml

@@ -1,25 +1,26 @@
 %h2 Seeds available to trade
 
-- if @seeds.length > 0
+- cache "interesting_seeds", :expires_in => 3.hours do
+  - if @seeds.length > 0
 
-  %table.table.table-striped
-    %tr
-      %th Owner
-      %th Crop
-      %th.hidden-phone.hidden-tablet Description
-      %th Will trade to
-      %th From location
-      %th
-
-    - @seeds.each do |seed|
+    %table.table.table-striped
       %tr
-        %td= link_to seed.owner.login_name, seed.owner
-        %td= link_to seed.crop.system_name, seed.crop
-        %td.hidden-phone.hidden-tablet= truncate(seed.description, :length => 40, :separator => ' ')
-        %td= seed.tradable? ? seed.tradable_to : ''
-        %td
-          - if seed.tradable?
-            = seed.owner.location.blank? ? "unspecified" : truncate(seed.owner.location, :length => 25, :separator => ', ')
-        %td= link_to 'Details', seed, :class => 'btn btn-mini'
+        %th Owner
+        %th Crop
+        %th.hidden-phone.hidden-tablet Description
+        %th Will trade to
+        %th From location
+        %th
+
+      - @seeds.each do |seed|
+        %tr
+          %td= link_to seed.owner.login_name, seed.owner
+          %td= link_to seed.crop.system_name, seed.crop
+          %td.hidden-phone.hidden-tablet= truncate(seed.description, :length => 40, :separator => ' ')
+          %td= seed.tradable? ? seed.tradable_to : ''
+          %td
+            - if seed.tradable?
+              = seed.owner.location.blank? ? "unspecified" : truncate(seed.owner.location, :length => 25, :separator => ', ')
+          %td= link_to 'Details', seed, :class => 'btn btn-mini'
 
 %p= link_to "View all seeds", seeds_path, :class => 'btn btn-primary'