I’m using the file_column plugin a lot. It lets you treat a file as an attribute on one of your models, and all you need to do to store it is provide a string column in your database table.

A lot of people have expressed concern that file_column doesn’t seem to have been worked on by it’s author at all this year. This maybe so, but don’t let that deter you from the fact that it is still currently the simplest and best way to handle images in rails applications.

One of the first snags that I’ve hit with file_column so far took me a few hours to nut out today, so I’d like to share it with you, gentle reader, in the hope that it might save you the same effort. I had a model object, which contained a file_column (and thus, potentially, a file), and I wanted to clone it. As a result of this, I wanted the new object to have it’s own separate copy of the file.

If you just naively copy the file_column (in my case, called “image”, on a model called “gift”), then file_column warns you that you’re just giving it a string, and thus you probably forgot a multipart declaration on your form. As you can see, file_column is pretty focussed on uploading files, not copying them between models.

Enough waffle, let’s just straight to my final clone method:

    def clone
      result = Gift.new(:name => name, :price => price, :description => description)
      unless image.nil?
        result.image = File.open(image)
        FileUtils.cp(image, result.image)
      end
      result
    end

The main bit of magic here is that I’m passing file_column (on the new object), a file object, rather than just a string. The file_column plugin has some basic support for this, but it’s pretty basic indeed. It seems that it can manage to copy the file out of the temp location into the final destination when I actually save the new model (not done inside clone), but it doesn’t copy it into the temp dir correctly (that normally happens on update. So, I put the copy in myself, and it all works.

You may not want to duplication your images on clone, but obviously this same technique is useful for any copying of file_column files between models, of the same or different model class.

When I get some “free” time (heheh), I’d like to do a bit of work on file column and fix this so that the hack isn’t needed, and perhaps look at some other design improvements. I’ve been through just about every line of it’s code this year on various projects, and while overall I’m greatly impressed, I think there’s more work that could be done to improve it.