Belongs to ​

field :user, as: :belongs_to

You will see three field types when you add a BelongsTo association to a model.

Options ​

-> searchable

class Avo::Resources::CourseLink < Avo::BaseResource
  def fields
    field :links,
      as: :has_many,
      searchable: true
  end
end

# app/avo/resources/course_link.rb
class Avo::Resources::CourseLink < Avo::BaseResource
  self.search = {
    query: -> {
      query.ransack(id_eq: params[:q], link_cont: params[:q], m: "or").result(distinct: false)
    }
  }
end

-> allow_via_detaching

-> attach_scope

field :user,
  as: :belongs_to,
  attach_scope: -> { query.non_admins }

-> polymorphic_as

-> types

-> polymorphic_help

-> use_resource

Overview ​

On the Index and Show views, Avo will generate a link to the associated record containing the @title value.

On the Edit and New views, Avo will generate a dropdown element with the available records where the user can change the associated model.

Polymorphic belongs_to ​

To use a polymorphic relation, you must add the polymorphic_as and types properties.

class Avo::Resources::Comment < Avo::BaseResource
  self.title = :id

  def fields
    field :id, as: :id
    field :body, as: :textarea
    field :excerpt, as: :text, show_on: :index do
      ActionView::Base.full_sanitizer.sanitize(record.body).truncate 60
    rescue
      ""
    end

    field :commentable, as: :belongs_to, polymorphic_as: :commentable, types: [::Post, ::Project]
  end
end

Polymorphic help ​

When displaying a polymorphic association, you will see two dropdowns. One selects the polymorphic type (Post or Project), and one for choosing the actual record. You may want to give the user explicit information about those dropdowns using the polymorphic_help option for the first dropdown and help for the second.

class Avo::Resources::Comment < Avo::BaseResource
  self.title = :id

  def fields
    field :id, as: :id
    field :body, as: :textarea
    field :excerpt, as: :text, show_on: :index do
      ActionView::Base.full_sanitizer.sanitize(record.body).truncate 60
    rescue
      ""
    end

    field :reviewable,
      as: :belongs_to,
      polymorphic_as: :reviewable,
      types: [::Post, ::Project, ::Team],
      polymorphic_help: "Choose the type of record to review",
      help: "Choose the record you need."
  end
end

Searchable belongs_to ​

There might be the case that you have a lot of records for the parent resource, and a simple dropdown won't cut it. This is where you can use the searchable option to get a better search experience for that resource.

class Avo::Resources::Comment < Avo::BaseResource
  self.title = :id

  def fields
    field :id, as: :id
    field :body, as: :textarea

    field :user, as: :belongs_to, searchable: true
  end
end

searchable works with polymorphic belongs_to associations too.

class Avo::Resources::Comment < Avo::BaseResource
  self.title = :id

  def fields
    field :id, as: :id
    field :body, as: :textarea

    field :commentable, as: :belongs_to, polymorphic_as: :commentable, types: [::Post, ::Project], searchable: true
  end
end

# app/avo/resources/post.rb
class Avo::Resources::Post < Avo::BaseResource
  self.search = {
    query: -> {
      query.ransack(id_eq: params[:q], name_cont: params[:q], body_cont: params[:q], m: "or").result(distinct: false)
    }
  }
end

# app/avo/resources/project.rb
class Avo::Resources::Project < Avo::BaseResource
  self.search = {
    query: -> {
      query.ransack(id_eq: params[:q], name_cont: params[:q], country_cont: params[:q], m: "or").result(distinct: false)
    }
  }
end

Belongs to attach scope ​

When you edit a record that has a belongs_to association, on the edit screen, you will have a list of records from which you can choose a record to associate with.

For example, a Post belongs to a User. So on the post edit screen, you will have a dropdown (or a search field if it's searchable) with all the available users. But that's not ideal. For example, maybe you don't want to show all the users in your app but only those who are not admins.

You can use the attach_scope option to keep only the users you need in the belongs_to dropdown field.

You have access to the query that you can alter and return it and the parent object, which is the actual record where you want to assign the association (the true Post in the below example).

# app/models/user.rb
class User < ApplicationRecord
  scope :non_admins, -> { where "(roles->>'admin')::boolean != true" }
end

# app/avo/resources/post.rb
class Avo::Resources::Post < Avo::BaseResource
  def fields
    field :user, as: :belongs_to, attach_scope: -> { query.non_admins }
  end
end

For scenarios where you need to add a record associated with that resource (you create a Post through a Category), the parent is unavailable (the Post is not persisted in the database). Therefore, Avo makes the parent an instantiated object with its parent populated (a Post with the category_id populated with the parent Category from which you started the creation process) so you can better scope out the data (you know from which Category it was initiated).

Allow detaching via the association ​

When you visit a record through an association, that belongs_to field is disabled. There might be cases where you'd like that field not to be disabled and allow your users to change that association.

You can instruct Avo to keep that field enabled in this scenario using allow_via_detaching.

class Avo::Resources::Comment < Avo::BaseResource
  self.title = :id

  def fields
    field :id, as: :id
    field :body, as: :textarea

    field :commentable,
      as: :belongs_to,
      polymorphic_as: :commentable,
      types: [::Post, ::Project],
      allow_via_detaching: true
  end
end