Templates only have one format. Before this commit, templates would be
constructed with a single element array that contained the format. This
commit eliminates the single element array and just implements a
`format` method. This saves one array allocation per template.
By default, variants in the templates will be picked up if a variant is set
and there's a match. The format will be:
app/views/projects/show.html.erb
app/views/projects/show.html+tablet.erb
app/views/projects/show.html+phone.erb
If request.variant = :tablet is set, we'll automatically be rendering the
html+tablet template.
In the controller, we can also tailer to the variants with this syntax:
class ProjectsController < ActionController::Base
def show
respond_to do |format|
format.html do |html|
@stars = @project.stars
html.tablet { @notifications = @project.notifications }
html.phone { @chat_heads = @project.chat_heads }
end
format.js
format.atom
end
end
end
The variant itself is nil by default, but can be set in before filters, like
so:
class ApplicationController < ActionController::Base
before_action do
if request.user_agent =~ /iPad/
request.variant = :tablet
end
end
end
This is modeled loosely on custom mime types, but it's specifically not
intended to be used together. If you're going to make a custom mime type,
you don't need a variant. Variants are for variations on a single mime
types.
