Rails File Upload and Content Types



You’re most likely going to deal with file uploads within your Rails application.  If you haven’t yet, it’s coming and hopefully this will save you some time.  I spent about an hour today racking my brain as to why I couldn’t validate different image types: image/jpeg, image/gif, and image/png.  I was doing a simple string check that looked like this:

def check_format
content_type = params[:photo].content_type
if content_type != “image/pjpeg” && content_type != “image/jpeg” && content_type != “image/gif” && content_type != “image/png”
“Error: You’ve specified the wrong file type”
end
end

This was failing repeatedly and even printing the content_type variable would yield image/jpeg.  It seemed that everything should work perfectly.  The only thing I could fathom is that there may be some extraneous garbage at the end of the string.  After doing a nice ruby chomp this solved the problem:

content_type = params[:photo].content_type.chomp

I hope this saves you some frustration in the future.



3 Responses to “Rails File Upload and Content Types”

1. gene says:

   December 21, 2006 at 2:19 pm

   damn… I wasted 2 hours no this. Thanks!
2. Chad says:

   February 15, 2007 at 5:01 pm

   I like to do it like this, using some built in feaurtes of ruby seems so much easier for me

   acceptable_types = ['image/jpeg', 'image/gif', 'image/png', ...etc..]
   “Err” unless acceptable_types.include?params[:photo].content_type.chomp
3. Waster says:

   May 31, 2007 at 8:47 am

   I wasted hours with this problem, then I googled “rails file content_type” and this came up. This needs to be filed as a bug.