Allow ransacker to have its arguments

[sineed]

This is related to #508 but I have another use case:

In my project I have Customer and Deal models. Customers have many Deals and each deal has amount attribute. I want to find customers which have made deals with total amount more than specified value for the last week. So my ransacker is:

# app/models/customer.rb
ransacker :sum_of_deals_last_week do |parent|
  deals_table = Deal.arel_table

  Arel::Nodes::Grouping.new(
    deals_table
      .project(Arel::Nodes::Sum.new([deals_table[:amount]]))
      .group(deals_table[:customer_id])
      .where(deals_table[:customer_id].eq(parent.table[:id])
        .and(deals_table[:created_at].gteq(1.week.ago.to_date)
          .and(deals_table[:created_at].lteq(Date.today))
        )
      ).ast
  )
end

And I can easily filter:

Customer.ransack(sum_of_deals_last_week_gt: 100)

The problem occurs when I want to change period of time. Say, for last month period I need to create new ransacker. What if I need to dynamically specify this period?

So with changes in this PR the following ransacker can be created:

# app/models/customer.rb
ransacker :sum_of_deals, args: [:parent, :rargs] do |parent, rargs|
  date_from = rargs[0]
  date_till = rargs[1]
  deals_table = Deal.arel_table

  Arel::Nodes::Grouping.new(
    deals_table
      .project(Arel::Nodes::Sum.new([deals_table[:amount]]))
      .group(deals_table[:customer_id])
      .where(deals_table[:customer_id].eq(parent.table[:id])
        .and(deals_table[:created_at].gteq(date_from)
          .and(deals_table[:created_at].lteq(date_till))
        )
      ).ast
  )
end

And I can use this ransacker:

Customer.ransack(
  c: [{
    a: { '0' => { name: :sum_of_deals, rargs: [1.week.ago.to_date, Date.today] } },
    p: :gt,
    v: [100]
  }]
)

[jonatack]

Thank you, @sineed. Would you like to update the change log and the wiki about this?

I'll admit I'm hesitant about the name rargs. How about a more self-explanatory name like ransacker_args?

[sineed]

@jonatack I've updated wiki page Using Ransackers and added #519

[jonatack]

@sineed thanks. The test and wiki example query generates the following SQL query, which does not seem to be valid SQL.

SELECT "people".* FROM "people" WHERE
  ((SELECT title FROM articles
    WHERE articles.person_id = people.id
    AND CHAR_LENGTH(articles.body) BETWEEN 10 AND 100
  )
  LIKE '%Rails has been released%') 
ORDER BY "people"."id" DESC

"PG::CardinalityViolation: ERROR: more than one row returned by a subquery used as an expression"

Could you create an example that generates valid SQL?

[melhotiby]

@sineed @jonatack How would this be used in a sort_link I have a sort link like the following

= sort_link @q, :read_items, 'Only Items Ive read'

ransacker :read_items, args: [:parent, :ransacker_args] do |parent, args|
  # Need args to have the current_user id
end

which I want to pass over the current_user id, is that possible with this? The wiki only does not make it clear on how to pass an argument like this

[sineed]

@jonatack
I've updated #519 and wiki. Please take a look.

@railsdevmatt
I don't use sorting functionality of ransack. And I don't know if a ransacker can be used as an attribute for sort_link method.
Ransacker arguments were implemented primary for advanced searching. And maybe it's possible to perform sorting without need of ransacker, can you add more info about your use case?

[melhotiby]

@sineed - Ok so i have a forum with topics

# forums controller
def show
  @forum = Forum.find(params[:id])
  @q = @forum.topics.ransack(params[:q])
  @topics = @q.result.page(params[:page])
end

# view show.html.haml
- unless @topics.empty?

  %ul
    %li= sort_link @q, :read_topics, 'Only topics Ive read'

  - @topics.each do |topic|
    ...
    ...

I want to pass in the current_user to the read_topics ransacker that i created and filter only the read topics. I do know this is possible without ransack, but figured if there was a way to accomplish this with a ransacker then I would give it a go.

[sineed]

@railsdevmatt Am I right if your topics have a have_and_belongs_to_many association with current_user' class? If so you can use https://github.com/activerecord-hackery/ransack#associations logic, something like this (say your association is named readers):

  link_to 'Only topics Ive read', forum_path(id: @forum.id, q: { readers_user_id: current_user.id })

[melhotiby]

@sineed - actually the relationship is like this

# topic model
class Topic < ActiveRecord::Base
  has_many :topic_reads, dependent: :destroy
  has_many :subscribers, through: :topic_subscriptions

class TopicRead < ActiveRecord::Base
  belongs_to :topic
  belongs_to :reader, class_name: "User", foreign_key: "reader_id"

class TopicSubscription < ActiveRecord::Base
  belongs_to :topic
  belongs_to :subscriber, -> { where "users.email != '' AND users.email IS NOT NULL" }, class_name: "Contact", foreign_key: "subscriber_id"

[jonatack]

The sort_link is for setting the order_by SQL via the Ransack :sorts (or :s) key.

Any filtering should be happening in your controller action (where you have ready access to current_user).

[reubenbrown]

@sineed @jonatack Love this feature! If I were constructing a ransack query in my controller like so (by "manually" merging together attribute names with predicates):

User.ransack({"s"=>"created_at desc", "created_at_eq"=>"2015-06-10"}).result

And I wanted to pass arguments to my ransacker for created_at

ransacker :created_at, args: [:parent, :ransacker_args] do |parent, args|
  start_time, end_time = args
  User.where('users.created_at > ? AND users.created_at < ?', start_time, end_time)
end

Is it possible to pass ransacker_args given the way I am constructing my query hash?

I've been playing around trying to properly include it in my hash but keep getting an undefined method error ransacker_args for the sort node. Since the documentation provides only one example of passing arguments to a ransacker it's a bit unclear if what I'm trying to do is even possible.