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module ActionController #:nodoc:
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module MimeResponds #:nodoc:
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def self.included(base)
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include ActionController::MimeResponds::InstanceMethods
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# Without web-service support, an action which collects the data for displaying a list of people
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# might look something like this:
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# @people = Person.find(:all)
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# Here's the same action, with web-service support baked in:
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# @people = Person.find(:all)
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# respond_to do |format|
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# format.xml { render :xml => @people.to_xml }
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# What that says is, "if the client wants HTML in response to this action, just respond as we
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# would have before, but if the client wants XML, return them the list of people in XML format."
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# (Rails determines the desired response format from the HTTP Accept header submitted by the client.)
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# Supposing you have an action that adds a new person, optionally creating their company
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# (by name) if it does not already exist, without web-services, it might look like this:
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# @company = Company.find_or_create_by_name(params[:company][:name])
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# @person = @company.people.create(params[:person])
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# redirect_to(person_list_url)
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# Here's the same action, with web-service support baked in:
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# company = params[:person].delete(:company)
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# @company = Company.find_or_create_by_name(company[:name])
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# @person = @company.people.create(params[:person])
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# respond_to do |format|
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# format.html { redirect_to(person_list_url) }
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# format.xml { render :xml => @person.to_xml(:include => @company) }
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# If the client wants HTML, we just redirect them back to the person list. If they want Javascript
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# (format.js), then it is an RJS request and we render the RJS template associated with this action.
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# Lastly, if the client wants XML, we render the created person as XML, but with a twist: we also
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# include the person's company in the rendered XML, so you get something like this:
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# Note, however, the extra bit at the top of that action:
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# company = params[:person].delete(:company)
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# @company = Company.find_or_create_by_name(company[:name])
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# This is because the incoming XML document (if a web-service request is in process) can only contain a
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# single root-node. So, we have to rearrange things so that the request looks like this (url-encoded):
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# person[name]=...&person[company][name]=...&...
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# And, like this (xml-encoded):
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# In other words, we make the request so that it operates on a single entity's person. Then, in the action,
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# we extract the company data from the request, find or create the company, and then create the new person
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# with the remaining data.
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# Note that you can define your own XML parameter parser which would allow you to describe multiple entities
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# in a single request (i.e., by wrapping them all in a single root node), but if you just go with the flow
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# and accept Rails' defaults, life will be much easier.
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# If you need to use a MIME type which isn't supported by default, you can register your own handlers in
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# environment.rb as follows.
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# Mime::Type.register "image/jpg", :jpg
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def respond_to(*types, &block)
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raise ArgumentError, "respond_to takes either types or a block, never both" unless types.any? ^ block
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block ||= lambda { |responder| types.each { |type| responder.send(type) } }
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responder = Responder.new(self)
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block.call(responder)
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class Responder #:nodoc:
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def initialize(controller)
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@controller = controller
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@request = controller.request
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@response = controller.response
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if ActionController::Base.use_accept_header
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@mime_type_priority = Array(Mime::Type.lookup_by_extension(@request.parameters[:format]) || @request.accepts)
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@mime_type_priority = [@request.format]
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def custom(mime_type, &block)
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mime_type = mime_type.is_a?(Mime::Type) ? mime_type : Mime::Type.lookup(mime_type.to_s)
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@responses[mime_type] ||= Proc.new do
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@response.template.template_format = mime_type.to_sym
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@response.content_type = mime_type.to_s
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block_given? ? block.call : @controller.send(:render, :action => @controller.action_name)
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def any(*args, &block)
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args.each { |type| send(type, &block) }
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custom(@mime_type_priority.first, &block)
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def self.generate_method_for_mime(mime)
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sym = mime.is_a?(Symbol) ? mime : mime.to_sym
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const = sym.to_s.upcase
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class_eval <<-RUBY, __FILE__, __LINE__ + 1
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def #{sym}(&block) # def html(&block)
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custom(Mime::#{const}, &block) # custom(Mime::HTML, &block)
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Mime::SET.each do |mime|
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generate_method_for_mime(mime)
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def method_missing(symbol, &block)
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mime_constant = Mime.const_get(symbol.to_s.upcase)
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if Mime::SET.include?(mime_constant)
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self.class.generate_method_for_mime(mime_constant)
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for priority in @mime_type_priority
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if priority == Mime::ALL
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@responses[@order.first].call
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if @responses[priority]
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@responses[priority].call
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return # mime type match found, be happy and return
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if @order.include?(Mime::ALL)
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@responses[Mime::ALL].call
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@controller.send :head, :not_acceptable