Can a mobile mime type fall back to “html” in Rails?

Question

I\'m using this code (taken from here) in ApplicationController to detect iPhone, iPod Touch and iPad requests:

before_filter :detect_mobile_request, :detec         


        

Answer 1

Trying removing the .html from the .html.erb and both iPhone and browser will fallback to the common file.

Answer 2

If your OS has symlinks you could use those.

$ ln -s show.html.erb show.mobile.erb

Answer 3

Rails 4.1 includes Variants, this is a great feature that allow you to set different views for the same mime. You can now simply add a before_action and let the variant to do the magic:

before_action :detect_device_variant

def detect_device_variant
  case request.user_agent
  when /iPad/i
    request.variant = :tablet
  when /iPhone/i
    request.variant = :phone
  end
end

Then, in your action:

respond_to do |format|
  format.json
  format.html               # /app/views/the_controller/the_action.html.erb
  format.html.phone         # /app/views/the_controller/the_action.html+phone.erb
  format.html.tablet do
    @some_tablet_specific_variable = "foo"
  end
end

More info here.

Answer 4

I solved this problem by using this before_filter in my ApplicationController:

def set_mobile_format
  request.formats.unshift(Mime::MOBILE) if mobile_client?
end

This puts the mobile format to the front of the list of acceptable formats. So, the Resolver prefers .mobile.erb templates, but will fall back to .html.erb if no mobile version is found.

Of course, for this to work you need to implement some kind of #mobile_client? function and put Mime::Type.register_alias "text/html", :mobile into your config/initializers/mime_types.rb

Answer 5

I need the same thing. I researched this including this stack overflow question (and the other similar one) as well as followed the rails thread (as mentioned in this question) at https://github.com/rails/rails/issues/3855 and followed its threads/gists/gems.

Heres what I ended up doing that works with Rails 3.1 and engines. This solution allows you to place the *.mobile.haml (or *.mobile.erb etc.) in the same location as your other view files with no need for 2 hierarchies (one for regular and one for mobile).

Engine and preparation Code

in my 'base' engine I added this in config/initializers/resolvers.rb:

    module Resolvers
      # this resolver graciously shared by jdelStrother at
      # https://github.com/rails/rails/issues/3855#issuecomment-5028260
      class MobileFallbackResolver < ::ActionView::FileSystemResolver
        def find_templates(name, prefix, partial, details)
          if details[:formats] == [:mobile]
            # Add a fallback for html, for the case where, eg, 'index.html.haml' exists, but not 'index.mobile.haml'
            details = details.dup
            details[:formats] = [:mobile, :html]
          end
          super
        end
      end
    end

    ActiveSupport.on_load(:action_controller) do
      tmp_view_paths = view_paths.dup # avoid endless loop as append_view_path modifies view_paths
      tmp_view_paths.each do |path|
        append_view_path(Resolvers::MobileFallbackResolver.new(path.to_s))
      end
    end

Then, in my 'base' engine's application controller I added a mobile? method:

    def mobile?
        request.user_agent && request.user_agent.downcase =~ /mobile|iphone|webos|android|blackberry|midp|cldc/ && request.user_agent.downcase !~ /ipad/
    end

And also this before_filter:

    before_filter :set_layout

    def set_layout
      request.format = :mobile if mobile?
    end

Finally, I added this to the config/initializers/mime_types.rb:

    Mime::Type.register_alias "text/html", :mobile

Usage

Now I can have (at my application level, or in an engine):

• app/views/layouts/application.mobile.haml
• and in any view a .mobile.haml instead of a .html.haml file.

I can even use a specific mobile layout if I set it in any controller: layout 'mobile'

which will use app/views/layouts/mobile.html.haml (or even mobile.mobile.haml).

Answer 6

You need to do several things to wire this up, but the good news is that Rails 3 actually makes this a lot simpler than it used to be, and you can let the router do most of the hard work for you.

First off, you need to make a special route that sets up the correct mime type for you:

# In routes.rb:
resources :things, :user_agent => /iPhone/, :format => :iphone
resources :things

Now you have things accessed by an iphone user agent being marked with the iphone mime type. Rails will explode at you for a missing mime type though, so head over to config/initializers/mime_types.rb and uncomment the iphone one:

Mime::Type.register_alias "text/html", :iphone

Now you're mime type is ready for use, but your controller probably doesn't yet know about your new mime type, and as such you'll see 406 responses. To solve this, just add a mime-type allowance at the top of the controller, using repsond_to:

class ThingsController < ApplicationController
  respond_to :html, :xml, :iphone

Now you can just use respond_to blocks or respond_with as normal.

There currently is no API to easily perform the automatic fallback other than the monkeypatch or non-mime template approaches already discussed. You might be able to wire up an override more cleanly using a specialized responder class.

Other recommended reading includes:

https://github.com/plataformatec/responders

http://www.railsdispatch.com/posts/rails-3-makes-life-better