Rails: Saving the contents of a binary field to a file

Question

I have a model with a binary field that contains a file. I'd like to save this file to disk as part of a process I need to do. For some reason, I can't find anything on how to do this.

The model contains a filename field and a file_contents field. I'd like to do something like this:

model = SomeModel.find :first
model.file_contents.save_to_file(model.filename)

Any help would be appreciated!

Answer 1

In ActiveRecord, the :binary type that you use to define your column type in your migration is going to map to a blob type in the database. So that wouldn't allow you to save to a file.

I think you would need to define a model class that is not a subclass of ActiveRecord::Base and define a custom save_to_file method for that class using the file i/o support in Ruby (the IO class and its subclass, File).

class SomeModel
 attr_accessor :file
 attr_accessor :contents

 def initialize
  @file = File.new("file.xyz", "w")
 end

 def save_and_close
  @file << contents
  @file.close
 end
end

Answer 2

I don't know why you'd want to call #save_to_file on the file contents instead of the model. Since you defined *file_contents* as an AR attribute I guess you want to save it to the DB and save it to disk. If that's the case you can simply add a method like this to your model:

 class YourModel < ActiveRecord::Base
   # ... your stuff ...
   def save_to_file
     File.open(filename, "w") do |f|
       f.write(file_contents)
     end
   end
 end

And then you'd simply do:

obj = YourModel.find(:first)
obj.save_to_file