warning: already initialized constant PDF

Question

Right now I am working on rails 3.0.0. If I run my project in terminal, I get this warning. Please help me.

/usr/share/ruby-rvm/gems/ruby-1.9.2-p290/gems/actionpack-3.0.0/lib/action_dispatch/http/mime_type.rb:98: warning: already initialized constant PDF

Cheddar

You might look in environment.rb to see if you have a PDF mime-type listed twice – Charmian

Are you using a PDF library such as Prawn? – Preceptor

are you using Wicked PDF? github.com/mileszs/wicked_pdf/pull/82 – Primatology

Answer 1

You might have this in your config/initializers/mime_types.rb file.

Mime::Type.register 'application/pdf', :pdf

It looks like newer versions of rails already registers it.

Oversweet

are you sure that rails registers it by default now? – Battement

No i'm not sure. It could also be caused by other gems registering it as well. – Oversweet

Yes, sure, it was added on 2011-06-27 in this commit github.com/rails/rails/commit/… – Ransdell

I had a similar problem. Even though I wasn't registering the :pdf mime type myself, one of the gems I was using was too old and still doing that. When I upgraded the gem to a later version, the error disappeared. If you can't find the source code, likely one of your gems is the culprit. – Hora

@AminAriana I had similar case but decided to solve it with re-registering the mime-type. For that I did Mime::Type.unregister(:csv) at first in mime-types initializer and after that registered csv-type again with desired new attributes. – Imprecate

Answer 2

Try using lookup_by_extenstion before defining it.

I have this on my config/initializers/mime_types.rb file.

Mime::Type.register "application/pdf", :pdf unless Mime::Type.lookup_by_extension(:pdf)

Bart

May not be necessary, but it's safer. Thanks! – Joletta

I was having the same error in Rails 3.2.14 using the Prawn gem. Changing Mime::Type.register "application/pdf", :pdf to Mime::Type.register "application/pdf", :pdf unless Mime::Type.lookup_by_extension(:pdf) did the trick! Thanks! – Cambric

Simply removing the Mime::Type.register 'application/pdf', :pdf gave me errors, but Mime::Type.register "application/pdf", :pdf unless Mime::Type.lookup_by_extension(:pdf) did the trick – Dispersive

You might want to extend that a bit to make sure the previous registration is actually identical to the one you are making: Mime::Type.register "application/pdf", :pdf unless Mime::Type.lookup_by_extension(:pdf) == "application/pdf" – Plasticity