Rails - How to paginate json associations, using as_json include/methods - ruby-on-rails

Let's say I have a Post that has many Comments. I have something like this in my model
class Post < AR:Base
...
PUBLIC_ATTRIBUTES = [:id, :title]
JSON_METHODS = [:comments]
...
def as_json(options={})
opts = {
only: PUBLIC_ATTRIBUTES,
methods: JSON_METHODS
}.merge(options){|k,o,n|o|n}
super(opts)
end
...
end
So in my controller I can just:
def show
post = Post.find ...
render json: { post: post }
end
JSON magically appears. The issue is when I have a lot of comments I want to paginate on. Also, the API is already in use, so people are using json[post][comments], otherwise i'd just add comments in like {post:post, comments:comments}, but that's a no-go.

Related

Using Rails Path and URL Helpers with fast_jsonapi

I would like to use the rails URL helper instead of hard coding the path to access the article.
I checked into the documentation but nothing is specified.
The article_path helper method exists (I checked by running rake routes)
class V3::ArticlesController < Api::V3::BaseController
def index
articles = Article.all
render json: ::V3::ArticleItemSerializer.new(articles).serialized_json
end
end
class V3::ArticleItemSerializer
include FastJsonapi::ObjectSerializer
attributes :title
link :working_url do |object|
"http://article.com/#{object.title}"
end
# link :what_i_want_url do |object|
# article_path(object)
# end
end
What you want to do is pass in the context to your serializer from your controller:
module ContextAware
def initialize(resource, options = {})
super
#context = options[:context]
end
end
class V3::ArticleItemSerializer
include FastJsonapi::ObjectSerializer
include ContextAware
attributes :title
link :working_url do |object|
#context.article_path(object)
end
end
class V3::ArticlesController < Api::V3::BaseController
def index
articles = Article.all
render json: ::V3::ArticleItemSerializer.new(articles, context: self).serialized_json
end
end
You should also switch to the jsonapi-serializer gem which is currently maintained as fast_jsonapi was abandoned by Netflix.
I found a solution thanks to max's example.
I also changed the gem to jsonapi-serializer
class V3::ArticlesController < Api::V3::BaseController
def index
articles = Article.all
render json: ::V3::ArticleItemSerializer.new(articles, params: { context: self }).serialized_json
end
end
class V3::ArticleItemSerializer
include JSONAPI::Serializer
attributes :title
link :working_url do |object|
"http://article.com/#{object.title}"
end
link :also_working_url do |object, params|
params[:context].article_path(object)
end
end

multiresources GET /search API implemented with JSONAPI

How would you implement a /search API that could return different resources with JSONAPI ?
GET /search?q=london could for example return an author resource for 'Jack London' and a book resource for 'London: The Novel'
I started doing this by implementing a search resource that would return included book and author resources but to follow JSONAPI, I'd have to refactor the API to GET /search?filger[q]=london
I have the feeling that this (quite common) usecase has not really been adressed by JSONAPI.
My final goal is to implement this with a Rails backend using JSONAPI::Resources and an ember app with ember-data
What would be your advice ?
You could do it manually using the jsonapi-utils gem so that you could point the resource you would like to use for the serialization:
With the jsonapi_serialize method:
class SearchesController < BaseController
def index
results = MySearchEngine.search(params)
render json: jsonapi_serialize(results, options: { resource: UserResource })
end
end
Or the high-level jsonapi_render method:
class SearchesController < BaseController
def index
results = MySearchEngine.search(params)
jsonapi_render json: results, options: { resource: UserResource }
end
end
Hope it helps.
Here's what I did:
# config/routes.rb
resource :search, only: [:show]
# app/controllers/searches_controller.rb
def show
render json: Search.new(params).as_json
end
# app/classes/search.rb
class Search
def initialize(params = {})
#results = [
Author.where(name: params[:q]),
Book.where(title: params[:q]),
].flatten
end
def as_json
serialized_resources =
#results.map do |result|
resource = JSONAPI::Resource.resource_for(result.model_name.singular)
serializer = JSONAPI::ResourceSerializer.new(resource)
serializer.serialize_to_hash(resource.new(result, nil))[:data]
end
{ data: serialized_resources }
end
end
Surely, there's a better way?

Save external Tweets in database in Rails

I am new to rails developement and to the MVC architecture. I have a little application where I can add Videos' URLs from Dailymotion or Youtube and get the tweets related to that URL using the twitter gem in Ruby on Rails.
Now i'm able to store the tweets like this : (This is the video controller)
def show
#video = Video.find(params[:id])
# Creating a URL variable
url = #video.url
# Search tweets for the given video/url
#search = get_client.search("#{#video.url} -rt")
# Save tweets in database
#search.collect do |t|
tweet = Tweet.create do |u|
u.from_user = t.user.screen_name.to_s
u.from_user_id_str = t.id.to_s
u.profile_image_url = t.user.profile_image_url.to_s
u.text = t.text.to_s
u.twitter_created_at = t.created_at.to_s
end
end
I'm not sure if this is the right way to do it (doing it in the controller ?), and what I want to do now is to specify that those tweets that have just been stored belong to the current video. Also I would like to have some sort of validation that makes the controller look in the database before doing this to only save the new tweets. Can someone help me with that ?
My models :
class Video < ActiveRecord::Base
attr_accessible :url
has_many :tweets
end
class Tweet < ActiveRecord::Base
belongs_to :video
end
My routes.rb
resources :videos do
resources :tweets
end
This is an example of a "fat controller", an antipattern in any MVC architecture (here's a good read on the topic).
Have you considered introducing a few new objects to encapsulate this behavior? For example, I might do something like this:
# app/models/twitter_search.rb
class TwitterSearch
def initialize(url)
#url = url
end
def results
get_client.search("#{#url} -rt")
end
end
# app/models/twitter_persistence.rb
class TwitterPersistence
def self.persist(results)
results.map do |result|
self.new(result).persist
end
end
def initialize(result)
#result = result
end
def persist
Tweet.find_or_create_by(remote_id: id) do |tweet|
tweet.from_user = screen_name
tweet.from_user_id_str = from_user_id
tweet.profile_image_url = profile_image_url
tweet.text = text
tweet.twitter_created_at = created_at
end
end
private
attr_reader :result
delegate :screen_name, :profile_image_url, to: :user
delegate :id, :user, :from_user_id, :text, :created_at, to: :result
end
Notice the use of find_or_create_by ... Twitter results should have a unique identifier that you can use to guarantee that you don't create duplicates. This means you'll need a remote_id or something on your tweets table, and of course I just guessed at the attribute name (id) that the service you're using will return.
Then, in your controller:
# app/controllers/videos_controller.rb
class VideosController < ApplicationController
def show
#tweets = TwitterPersistence.persist(search.results)
end
private
def search
#search ||= TwitterSearch.new(video.url)
end
def video
#video ||= Video.find(params[:id])
end
end
Also note that I've removed calls to to_s ... ActiveRecord should automatically convert attributes to the correct types before saving them to the database.
Hope this helps!

Including virtual attributes when responding_to a JSON call

I have a post model that has a virtual attribute that I would like to set and then include in a response to a JSON call to my post#index action. I can't seem to get the virtual attribute to be included in the response.
class Post < ActiveRecord::Base
attr_accessible :height
attr_accessor :m_height
end
class PostsController < ApplicationController
respond_to :html, :json, :js
def index
story = Story.find(params[:story_id])
#posts = story.posts.where("posts.id >= ?", 100)
#posts.each do |post|
post.m_width = post.height * 200
end
results = { :total_views => story.total_views,
:new_posts => #posts }
respond_with(results)
end
end
I think that I must need something similar to #post.to_json(:methods => %w(m_width)), but I don't see how to use :methods in a respond_with
This seems to provide the answer. Implement a to_json and to_xml in your models, as appropriate, with definitions like:
There's a better answer implied here.
Following code stolen from the post:
def as_json(options={})
super(options.merge(:methods => [...], :only => [...], :include => [...])
end
to_json won't be called on your model in this case, from what I can tell in the source, but as_json will be, in the process of serialization.
So, here's what happens, in overview form:
You call respond_with with the results hash you've constructed.
Rails (ActionController) calls to_json on that.
to_json sends you over to JSON::Encoding which keeps calling as_json all the way down until everything is JSONified.
That's why there was the confusion about to_json and as_json in an earlier version of this answer.

Rails 3: alias_method_chain to set specific attribute first

When user's create a post I'd like to set the user_id attribute first. I'm trying to do this using alias_method_chain on the arrtibutes method. But I'm not sure if this is right as the problem I thought this would fix is still occurring. Is this correct?
Edit:
When my users create a post they assign 'artist(s)' to belong to each post, using a virtual attribute called 'artist_tokens'. I store the relationships in an artist model and a joined table of artist_ids and post_ids called artisanships.
I'd like to to also store the user_id of whomever created the artist that belongs to their post (and I want it inside the artist model itself), so I have a user_id column on the artist model.
The problem is when I create the artist for each post and try to insert the user_id of the post creator, the user_id keeps showing as NULL. Which is highly likely because the post's user_id attribute hasn't been set yet.
I figured to get around this I needed to set the user_id attribute of the post first, then let the rest of the attributes be set as they normally are. This is where I found alias_method_chain.
post.rb
attr_reader :artist_tokens
def artist_tokens=(ids)
ids.gsub!(/CREATE_(.+?)_END/) do
Artist.create!(:name => $1, :user_id => self.user_id).id
end
self.artist_ids = ids.split(",")
end
def attributes_with_user_id_first=(attributes = {})
if attributes.include?(:user_id)
self.user_id = attributes.delete(:user_id)
end
self.attributes_without_user_id_first = attributes
end
alias_method_chain :attributes=, :user_id_first
EDIT:
class ArtistsController < ApplicationController
def index
#artists = Artist.where("name like ?", "%#{params[:q]}%")
results = #artists.map(&:attributes)
results << {:name => "Add: #{params[:q]}", :id => "CREATE_#{params[:q]}_END"}
respond_to do |format|
format.html
format.json { render :json => results }
end
end
In your controller, why not just do this:
def create
#post = Post.new :user_id => params[:post][:user_id]
#post.update_attributes params[:post]
...
end
But it seems to me that it would be much better to create the artist records after you've done validation on the post rather than when you first assign the attribute.
EDIT
I would change this to a callback like this:
class Post < ActiveRecord::Base
attr_accessor :author_tokens
def artist_tokens=(tokens)
#artist_tokens = tokens.split(',')
end
after_save :create_artists
def create_artists
#artist_tokens.each do |token|
...
end
end
end

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