asset_path helper erroring in method

Question

I am creating a method on my model that I can use to return the URL to the correct logo, photo or a fallback image. My code is:

def image
    if photo1.attached?
        { url: photo1.url, alt: "Photo of #{full_name}" }
    elsif photos.any?
        photo = photos.first
        url = photo.url(:large_square)
        { url: url, alt: "Photo of #{full_name}" }
    else
        { url: url_for(asset_path "placeholder.svg"), alt: "Placeholder for #{full_name}" }
    end
end

But it's erroring with url_for and asset_path and i'm unsure how to resolve it?

Answer 1

You can Rails.application.routes.url_helpers and ActionView::Helpers::AssetUrlHelper

You can include these modules to some class

class MyClass
  include Rails.application.routes.url_helpers
  include ActionView::Helpers::AssetUrlHelper

  def my_url
    url_for(asset_path("placeholder.svg"))
  end
end

and MyClass.new.my_url will return path

See also this answer:

It is possible to use helpers with ActionController::Base.helpers or (and) with Rails.application.routes.url_helpers

For example

helpers = ActionController::Base.helpers
url_helpers = Rails.application.routes.url_helpers

helpers.link_to "Root_path", url_helpers.root_path
# => "<a href=\"/\">Root_path</a>"

But probably it is not good idea to define such methods in the models because they shouldn't know something about URLs and frontend assets. Maybe it's better to think about helpers or decorators for this purpose