Belongs to ​
field :user, as: :belongs_to
You will see three field types when you add a BelongsTo
association to a model.
Options ​
-> searchable
Turns the attach field/modal from a select
input to a searchable experience
class Avo::Resources::CourseLink < Avo::BaseResource
def fields
field :links,
as: :has_many,
searchable: true
end
end
WARNING
Avo uses the search feature behind the scenes, so make sure the target resource has the search_query
option configured.
# 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
Default ​
false
Possible values ​
true
, false
-> allow_via_detaching
Keeps the field enabled when visiting from the parent record.
Default ​
false
Possible values ​
true
, false
-> attach_scope
Scope out the records the user sees on the Attach modal.
Default ​
nil
Possible values ​
field :user,
as: :belongs_to,
attach_scope: -> { query.non_admins }
Pass in a block where you attach scopes to the query
object. The block is executed in the ExecutionContext
.
-> polymorphic_as
Sets the field as polymorphic with the key set on the model.
Default ​
nil
Possible values ​
A symbol, used on the belongs_to
association with polymorphic: true
.
-> types
Sets the types the field can morph to.
Default ​
[]
Possible values ​
[Post, Project, Team]
. Any array of model names.
-> polymorphic_help
Sets the help text for the polymorphic type dropdown. Useful when you need to specify to the user why and what they need to choose as polymorphic.
Default ​
nil
Possible values ​
Any string.
-> use_resource
Sets a different resource to be used when displaying (or redirecting to) the association table.
Default ​
nil
. When nothing is selected, Avo infers the resource type from the reflected association.
Possible values ​
Avo::Resources::Post
, Avo::Resources::PhotoComment
, or any Avo resource class.
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
​
Watch the demo video 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
INFO
Avo uses the search feature behind the scenes, so make sure the target resource has the query
option configured inside the search
block.
# 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 ​
Watch the demo videoWhen 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