Doesn't support source & output files that are directly contained by the Fedora object about hydra-derivatives HOT 13 CLOSED

@flyingzumwalt seems like the solution should be that hydra-derivatives accepts parameters for these. Is the gem currently making too many assumptions about the model?

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@awead one solution would be to use .send instead of .attached_files, but I bet there is a reason that it didn't already do that?

Example

def source_file
    object.send(source_name.to_sym)
end

instead of

def source_file
    object.attached_files[source_name.to_s]
end

from hydra-derivatives.

or maybe rely on a retrieve_attached_file method

def retrieve_attached_file(object, attachment_ref)
    object.send(attachment_ref.to_sym)
end

def source_file
    retrieve_attached_file(object, source_name)
end

def output_file(path)
        # first, check for a defined file
        output_file = if retrieve_attached_file(object, path)
          object.attached_files[path]
        else
          ActiveFedora::File.new("#{object.uri}/#{path}").tap do |file|
            object.attach_file(file, path)
          end
        end
      end

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I would love it if hydra-derivatives didn't assume that you were using fedora at all. Let the object know how persistence happens, and let the calls to transform_file tell hydra-derivatives which methods to call on that object in order to retrieve the source and return the output.

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Then hydra-derivatives would become the first hydra gem that's truly useful outside of the hydra/fedora sphere.

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👍 to that.

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@flyingzumwalt specify a default retrieve_attached_file method that is the current process using attached_files, but the implementor overrides that? Or make it explicit:

class Hydra::Derivatives::Processor::Base

  def retrieve_attached_file
    raise NotImplementedError, "You must specify a method for retrieving the file's content"
  end

end

from hydra-derivatives.

That doesn't work. That would mean all of your Processors have to choose
which attached_file strategy to assume. I should be able to use the Image
processor, etc. regardless of how files are attached to my object.

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fair enough!

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👍 to this work, hydra-derivatives assumptions about the model keep us from adopting it.

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Solving this by refactoring Processors to use a RetrieveSourceFile service for retrieving source file and a PersistOutputFile service for persisting output file. These services can be configured in the initializer and/or in your calls to transform_file.

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See f48c2e5, 946f581.

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Fixed in #61. Test coverage in #66.

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