Ruby/Rails Collection to Collection

Ruby/Rails Collection to Collection

l = Library.find(:all, :include => :books)
l.books.map { |b| b.library_ids }.flatten.uniq

Note that map(&:library_ids) is slower than map { |b| b.library_ids } in Ruby 1.8.6, and faster in 1.9.0.

I should also mention that if you used :joins instead of include there, it would find the library and related books all in the same query speeding up the database time. :joins will only work however if a library has books.

Rails activerecord get collection of collection

You can use has many through to get rails to do the joins for you.

class User
  has_many :events
  has_many :advertisements, through: :events
end

user = User.first
user_ads = user.advertisements

If you don't want to do that though you can do

user = User.first
ads = Advertisement.joins(:event).where(events: { user_id: user.id })

How to collect a collection of objects that are contained in the current month

If you already have an assignment where to take the date from, you can get the first and last day of that month:

assigment_date = assignment.date.to_date
Assignment.where(date: assignment_date.beginning_of_month..assignment_date.end_of_month)

ruby rails - getting a collection of objects from a collection of foreign keys

You have two options for preserving order. First - eager load users in original query. In this case

users = @results.map(&:user)

Second - reorder on ruby side

idx = User.find(@results.map(&:user_id)).index_by(&:id)
users = @result.map{|r| idx[r.use_id]}

Rails: Iterate over collection within a Model's Class Method

Reverse your logic and let the database do the work. If all of them have a number_val of 999 then none of them have a number_val that is not 999 and this is easily expressed:

def self.all_have_number_value_999
  !where.not(:number_val => 999).exists?
end

That will be a single fairly efficient database query.

Since this is a class method and class methods are mixed into relations (scopes are pretty much specific types of class methods after all), you can call this method on a relation and things like:

Foo.where(id: [123, 456]).all_have_number_value_999?

should work as would Foo.all_have_number_value_999?.

---

If you want to perform some arbitrary logic while iterating over the collection outside the database, then you could throw in an all call to resolve the query before iterating:

def self.all_have_number_value_999?
  all.each do |foo_object|
    ...
  end
end

rails 5 collection select

class Document < ApplicationRecord
 has_many :entries
end

class Entry < ApplicationRecord
 belongs_to :document
end

In your view file like: new.html.erb

 <%= f.select :document_id, Document.all.collect { |p| p.id }, include_blank: true %>

Multiple select in collection

app/models/your_model.rb:

class YourModel < ApplicationRecord
  serialize :activity, Array # add this

  # you can't use `inclusion:` validation because it is only for validating a single value
  # so you'll do something like this, or if you want it to clean it a bit by defining a method instead, see here https://stackoverflow.com/questions/13579357/validates-array-elements-inclusion-using-inclusion-in-array
  validate do
    unless %w(Vente Location Syndic Gestion).include? activity
      errors.add(:activity, "#{activity} n'est pas un mandat valide"
    end
  end
end

app/views/.../some_view.html.erb:

<%= f.input :activity,
      required: true,
      autofocus: true,
      label: "Votre Activité",
      collection: ["Vente", "Location", "Gestion", "Syndic"],
      input_html: { multiple: true },
      include_hidden: false
%>

• I added input_html: { multiple: true } above so that the params will be an array of values instead of just a single value

• I added that include_hidden: false above because without it you'll get something like

  ["", "Location", "Syndic"]
  

  which adds an empty string instead of just..

  ["Location", "Syndic"]
  

  • more info here

app/controllers/some_controller.rb:

devise_parameter_sanitizer.permit(
  :account_update,
  keys: [
    :password,
    :password_confirmation,
    :photo,
    :address,
    :cover,
    activity: [] # change this from :activity
  )

Tested working

Rails: Query to get collection associated with collection

You just want to get all associated PlaceOfUseAreas objects in single query, right?

If so, Rails have pretty single line solution for it:

PlaceOfUseArea.joins(:water_wights).uniq

Read more about joins method if you want more information.

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