Url_for helper for polymorphic paths

[Xosmond]

What should people do when need to generate a url base on a object?

On rails I use url_for(object), but in lucky i can't use Controller::Action.with(object), because I don't know which action or controller it would be.

Is there any way now to solve this? Or maybe should I go to checkout Active record to see how its implemented?

[paulcsmith]

@Xosmond Can you give a full example of what you mean? My guess would be that you add a method to the objects that returns the action you want. For example:

class Author < User
  def route
    Author::Show.with(self)
  end
end

class Admin < User
  def route
    Admin::Show.with(self)
  end
end

link to: user.route # Uses the right action depending on the whether the user is an Admin or an Author

Does that help?

[Xosmond]

Yes, that helps but how to make it a default behavior?, because I think that would be a method on every class.

class Authors::Show < BrowserAction
  action do
    render user: AuthorQuery.new.find(id)
  end
end

class Author
  def route
    (self.class.name.pluralize.contantize)::Show.with(self).path
  end
end

But pluralize and constantize doesn't seem to work. (Ruby background here)
https://play.crystal-lang.org/#/r/33oh
Pluralize and Constantize seem to come with ActiveSupport

[paulcsmith]

@Xosmond That can't be done at runtime, but it can be done at compile time:

# https://play.crystal-lang.org/#/r/33sm
class Users::Show
  def self.with(id)
    # generate a route
  end
end

# Probably put it in `src/models/mixins/routeable.cr
module Routeable
  macro included
    # https://crystal-lang.org/docs/syntax_and_semantics/macros.html
    def route
      {{ "#{@type.name}s".id }}::Show.with(self)
    end
  end
end

class User
  include Routeable
end

User.new.route

I think that should work. This is something that could be added to Lucky for all models, but before I do, can you explain what the full use case is? Preferably with a bit of code from your app? I'd like to see if there is some other way of doing this that's better or if this is the best approach. Thanks!

[Xosmond]

Thanks for your help. I trying to move an rails app to crystal with lucky framework and I have a basic case of notifications that I use to redirect the user to action object.

On the view for each notification:

<li class="notif-info" data-id="<%= notification.id %>" style="cursor: pointer;" onclick="window.location='<%= url_for(notification.notifiable) %>';">
  <div class="dropdown-messages-box">
    <div class="media-body">
      <%= notification.message %>. <br/>
      <small class="text-navy"><%= notification.created_at.strftime("%l:%M %p %d/%m/%y") %></small>
    </div>
  </div>
</li>
<li class="divider"></li>

The notification model in ruby:

# notification.rb
class Notification < ApplicationRecord
  belongs_to :recipient, class_name: "User"
  belongs_to :actor, class_name: "User", optional: true
  belongs_to :notifiable, polymorphic: true

  scope :unread, ->{ where(read_at: nil) }
end
 

By now I just was trying to have the base view:

# src/pages/main_layout.cr
...
  def render_notification(notification)
    li class:"notif-info", data-id: notification.id.to_s, style:"cursor: pointer;", onclick:"window.location='#{notification.notifiable.route.path}';" do
      div class:"dropdown-messages-box" do
        div class: "media-body" do
          notification.message
          br
          small class: "text-navy" do
            notification.created_at.to_s("%l:%M %p %d/%m/%y")
          end
        end
      end
    end
    li class: "divider"
  end

But with your code, could be:

# src/models/mixins/routeable.cr
module Routeable
  macro included
    def route
      {{ "#{@type.name}s".id }}::Show.with(self)
    end
  end
end

# src/models/base_model.cr
abstract class BaseModel < LuckyRecord::Model
  include Routeable
end

The notification model:

# notification.cr
class Notification < BaseModel
  belongs_to recipient : User
  belongs_to  actor : User
  belongs_to notifiable : BaseModel, polymorphic: true # Here I have the real problem

end

Query class:

class NotificationQuery < Notification::BaseQuery
  def unread
    read_at(nil)
  end
end

The only problem with route would be the pluralization, in this case we are only adding an "s", but compilation would raise an error if there is a problem.

Now the polymorphic option is the real thing, (This issue would go on lucky/record repo). How to get the class, because we can't on compilation time, it depends of the class instance.

[actsasflinn]

@Xosmond pluralization is now present in LuckySupport::Inflector https://github.com/luckyframework/support

Looks like Constantize isn't possible in crystal currently but looks like you might have the start of a nice workaround.

I wonder if there's a intermediary routing table approach for predefining and referencing routes without the need to know the full scope of the action.

[paulcsmith]

@Xosmond That is a really nice example. I think the route stuff is handled with the snippet I gave you, but the associations stuff is a bit trickier. I'd like to handle belongs_to_polymorphic, but in the meantime I think this can work:

table :notifications do
  field notifiable_type : String
  field notifiable_id : Int32
end

def notifiable : Comment | SomeOtherNotifiable
  case notifiable_type
  when "comment"
   CommentQuery.new.find(notifiable_id)
  end
end

# And in forms you'd do this
NotificationForm.new(notifiable_type: "comment", notifiable_id: comment.id).save

This is less than ideal, but I think it will work as a stop-gap solution. Let me know what you think and if it works :)