api: support the expiry param on all GET requests.

app/controllers/artists_controller.rb

@@ -44,7 +44,6 @@ class ArtistsController < ApplicationController
       end
       format.json do
         render :json => @artists.to_json(:include => [:urls])
-        expires_in params[:expiry].to_i.days if params[:expiry]
       end
     end
   end

app/controllers/pools_controller.rb

@@ -18,12 +18,7 @@ class PoolsController < ApplicationController
 
   def index
     @pools = Pool.includes(:creator).search(search_params).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
-    respond_with(@pools) do |format|
-      format.json do
-        render json: @pools.to_json
-        expires_in params[:expiry].to_i.days if params[:expiry]
-      end
-    end
+    respond_with(@pools)
   end
 
   def gallery

app/controllers/tags_controller.rb

@@ -21,8 +21,6 @@ class TagsController < ApplicationController
       @tags = Tag.names_matches_with_aliases(params[:search][:name_matches])
     end
 
-    expires_in params[:expiry].to_i.days if params[:expiry]
-
     respond_with(@tags, root: "tags")
   end
 

app/controllers/users_controller.rb

@@ -30,12 +30,7 @@ class UsersController < ApplicationController
       redirect_to user_path(@user)
     else
       @users = User.search(search_params).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
-      respond_with(@users) do |format|
-        format.json do
-          render json: @users.to_json
-          expires_in params[:expiry].to_i.days if params[:expiry]
-        end
-      end
+      respond_with(@users)
     end
   end
 

app/controllers/wiki_pages_controller.rb

@@ -26,10 +26,6 @@ class WikiPagesController < ApplicationController
           end
         end
       end
-      format.json do
-        render json: @wiki_pages.to_json
-        expires_in params[:expiry].to_i.days if params[:expiry]
-      end
     end
   end
 

app/logical/application_responder.rb

@@ -3,6 +3,11 @@
 class ApplicationResponder < ActionController::Responder
   # this is called by respond_with for non-html, non-js responses.
   def to_format
+    if get?
+      expiry = request.params["expiry"]
+      controller.expires_in expiry.to_i.days if expiry.present?
+    end
+
     if format == :xml
       options[:root] ||= resource.table_name.dasherize if resource.respond_to?(:table_name)
     end

test/functional/application_controller_test.rb

@@ -192,6 +192,13 @@ class ApplicationControllerTest < ActionDispatch::IntegrationTest
       assert_equal(tags.first.id, response.parsed_body.first.fetch("id"))
     end
 
+    should "support the expiry parameter" do
+      get posts_path, as: :json, params: { expiry: "1" }
+
+      assert_response :success
+      assert_equal("max-age=#{1.day}, private", response.headers["Cache-Control"])
+    end
+
     should "return the correct root element name for empty xml responses" do
       get tags_path, as: :xml