Merge pull request #294 from nikz/add-links-option-to-relationship-serializer

Adds a :links option to the relationship macros

README.md

@@ -245,15 +245,38 @@ class MovieSerializer
 end
 ```
 
-### Meta Per Resource
-
-For every resource in the collection, you can include a meta object containing non-standard meta-information about a resource that can not be represented as an attribute or relationship.
+#### Links on a Relationship
 
+You can specify [relationship links](http://jsonapi.org/format/#document-resource-object-relationships) by using the `links:` option on the serializer. Relationship links in JSON API are useful if you want to load a parent document and then load associated documents later due to size constraints (see [related resource links](http://jsonapi.org/format/#document-resource-object-related-resource-links))
 
 ```ruby
 class MovieSerializer
   include FastJsonapi::ObjectSerializer
 
+  has_many :actors, links: {
+    self: :url,
+    related: -> (object) {
+      "https://movies.com/#{object.id}/actors"
+    }
+  }
+end
+```
+
+This will create a `self` reference for the relationship, and a `related` link for loading the actors relationship later. NB: This will not automatically disable loading the data in the relationship, you'll need to do that using the `lazy_load_data` option:
+
+```ruby
+  has_many :actors, lazy_load_data: true, links: {
+    self: :url,
+    related: -> (object) {
+      "https://movies.com/#{object.id}/actors"
+    }
+  }
+```
+
+### Meta Per Resource
+
+For every resource in the collection, you can include a meta object containing non-standard meta-information about a resource that can not be represented as an attribute or relationship.
+```ruby
   meta do |movie|
     {
       years_since_release: Date.current.year - movie.year

lib/fast_jsonapi/object_serializer.rb

@@ -257,7 +257,9 @@ module FastJsonapi
           cached: options[:cached],
           polymorphic: fetch_polymorphic_option(options),
           conditional_proc: options[:if],
-          transform_method: @transform_method
+          transform_method: @transform_method,
+          links: options[:links],
+          lazy_load_data: options[:lazy_load_data]
         )
       end
 

lib/fast_jsonapi/relationship.rb

@@ -1,6 +1,6 @@
 module FastJsonapi
   class Relationship
-    attr_reader :key, :name, :id_method_name, :record_type, :object_method_name, :object_block, :serializer, :relationship_type, :cached, :polymorphic, :conditional_proc, :transform_method
+    attr_reader :key, :name, :id_method_name, :record_type, :object_method_name, :object_block, :serializer, :relationship_type, :cached, :polymorphic, :conditional_proc, :transform_method, :links, :lazy_load_data
 
     def initialize(
       key:,
@@ -14,7 +14,9 @@ module FastJsonapi
       cached: false,
       polymorphic:,
       conditional_proc:,
-      transform_method:
+      transform_method:,
+      links:,
+      lazy_load_data: false
     )
       @key = key
       @name = name
@@ -28,14 +30,19 @@ module FastJsonapi
       @polymorphic = polymorphic
       @conditional_proc = conditional_proc
       @transform_method = transform_method
+      @links = links || {}
+      @lazy_load_data = lazy_load_data
     end
 
     def serialize(record, serialization_params, output_hash)
       if include_relationship?(record, serialization_params)
         empty_case = relationship_type == :has_many ? [] : nil
-        output_hash[key] = {
-          data: ids_hash_from_record_and_relationship(record, serialization_params) || empty_case
-        }
+
+        output_hash[key] = {}
+        unless lazy_load_data
+          output_hash[key][:data] = ids_hash_from_record_and_relationship(record, serialization_params) || empty_case
+        end
+        add_links_hash(record, serialization_params, output_hash) if links.present?
       end
     end
 
@@ -96,6 +103,12 @@ module FastJsonapi
       record.public_send(id_method_name)
     end
 
+    def add_links_hash(record, params, output_hash)
+      output_hash[key][:links] = links.each_with_object({}) do |(key, method), hash|
+        Link.new(key: key, method: method).serialize(record, params, hash)\
+      end
+    end
+
     def run_key_transform(input)
       if self.transform_method.present?
         input.to_s.send(*self.transform_method).to_sym

spec/lib/object_serializer_relationship_links_spec.rb

@@ -0,0 +1,71 @@
+require 'spec_helper'
+
+describe FastJsonapi::ObjectSerializer do
+  include_context 'movie class'
+
+  context "params option" do
+    let(:hash) { serializer.serializable_hash }
+
+    context "generating links for a serializer relationship" do
+      let(:params) { {  } }
+      let(:options_with_params) { { params: params } }
+      let(:relationship_url) { "http://movies.com/#{movie.id}/relationships/actors" }
+      let(:related_url) { "http://movies.com/movies/#{movie.name.parameterize}/actors/" }
+
+      before(:context) do
+        class MovieSerializer
+          has_many :actors, lazy_load_data: false, links: {
+            self:    :actors_relationship_url,
+            related: -> (object, params = {}) {
+              "#{params.has_key?(:secure) ? "https" : "http"}://movies.com/movies/#{object.name.parameterize}/actors/"
+            }
+          }
+        end
+      end
+
+      context "with a single record" do
+        let(:serializer) { MovieSerializer.new(movie, options_with_params) }
+        let(:links) { hash[:data][:relationships][:actors][:links] }
+
+        it "handles relationship links that call a method" do
+          expect(links).to be_present
+          expect(links[:self]).to eq(relationship_url)
+        end
+
+        it "handles relationship links that call a proc" do
+          expect(links).to be_present
+          expect(links[:related]).to eq(related_url)
+        end
+
+        context "with serializer params" do
+          let(:params) { { secure: true } }
+          let(:secure_related_url) { related_url.gsub("http", "https") }
+
+          it "passes the params to the link serializer correctly" do
+            expect(links).to be_present
+            expect(links[:related]).to eq(secure_related_url)
+          end
+        end
+      end
+
+    end
+
+    context "lazy loading relationship data" do
+      before(:context) do
+        class LazyLoadingMovieSerializer < MovieSerializer
+          has_many :actors, lazy_load_data: true, links: {
+            related: :actors_relationship_url
+          }
+        end
+      end
+
+      let(:serializer) { LazyLoadingMovieSerializer.new(movie) }
+      let(:actor_hash) { hash[:data][:relationships][:actors] }
+
+      it "does not include the :data key" do
+        expect(actor_hash).to be_present
+        expect(actor_hash).not_to have_key(:data)
+      end
+    end
+  end
+end

spec/shared/contexts/movie_context.rb

@@ -61,6 +61,10 @@ RSpec.shared_context 'movie class' do
       def url
         "http://movies.com/#{id}"
       end
+
+      def actors_relationship_url
+        "#{url}/relationships/actors"
+      end
     end
 
     class Actor