Madmin and Shrine (and its fake attributes)

[johlym]

I'm not sure if I'm even correctly understanding what I'm seeing. Long and short is I'm attempting to implement Shrine. All is well until I get to the stage where I have to tell Madmin that I need a hidden field and real field to appear. Their example is simple:

form_for @photo do |f|
  f.hidden_field :image, value: @photo.cached_image_data
  f.file_field :image
  f.submit
end

Seems simple enough for sure, but the field Shrine wants defined doesn't actually have a dedicated attribute in the model... it's fake... or as Shrine calls it, virtual.

This poses a problem when Madmin tries to render the form and gives me something to the effect of:

Madmin couldn't find attribute or association 'image' on Ad model.

I do not doubt it couldn't find it, because it's not real. Any ideas on how I can get around this? I had to shelve ActiveStorage for this project because it lacked public URL support without lots of hacks. I'm thinking I might have unknowingly traded one set of hacks for another.

[excid3]

You'll want to specify the field type manually for now. field :image, field: Fields::Attachment. This is mainly for ActiveStorage attachments, but it might need a custom field since Attachment may not render the correct URL since it functions differently.

If someone wants, we could make a PR that:

• Modifies infer_type in Resource to check for a Shrine value from the method
• Either update Field::Attachment to also support Shrine uploads or add a Field::Image type that knows how to render the URL

[johlym]

Thanks for replying so quickly! Maybe I'm not grokking the proper way to make this happen. setting:

class AdResource < Madmin::Resource
  ...
  attribute :image, field: Fields::Attachment
  ...
end

I get

uninitialized constant AdResource::Fields

Am I misinterpreting your workaround?