If you want to use AFMotion with status code and errors, try this file.

api.rb

class Api
  class << self
    # Init API server, with the shared client
    def init_server
      if Auth.needlogin?
        AFMotion::SessionClient.build_shared(BASE_URL) do
          session_configuration :default

          header "Accept", "application/json"

          response_serializer :json
        end
      else
        AFMotion::SessionClient.build_shared(BASE_URL) do
          session_configuration :default

          header "Accept", "application/json"
          header "X-Api-Email",  Auth.email
          header "X-Api-Token",  Auth.token

          response_serializer :json
        end
      end
    end

    METHODS = %w(get post).freeze
    # Api.post "auth/login", data do |result, error|
    #   if result
    # =>
    #   end
    #   if error
    #     App.alert(error["title"], {cancel_button_title: "Got it!", message: error["message"]})
    #   end
    # end
    METHODS.each do |method|
      define_method method do |path, parameters=nil, *args, &block|
        AFMotion::SessionClient.shared.send(method, path, parameters) do |result|
          p result
          if result.success?
            block.call(result.object, nil) if block
          else
            if result.error.userInfo[AFNetworkingOperationFailingURLResponseErrorKey]
              error_headers = result.error.userInfo[AFNetworkingOperationFailingURLResponseErrorKey].allHeaderFields
            end
            if result.error.userInfo[AFNetworkingOperationFailingURLResponseErrorKey]
              error_code = result.error.userInfo[AFNetworkingOperationFailingURLResponseErrorKey].statusCode
              error_code_local = NSHTTPURLResponse.localizedStringForStatusCode(error_code)
              error = result.error.userInfo[AFNetworkingOperationFailingURLResponseDataErrorKey]
            end
            if error_code && error_code.to_s =~ /404/
              # block.call(nil, "The request is not found (404).") if block
              block.call(nil, {"message" => "The request is not found (404)."}) if block
            elsif error_code && error_code.to_s =~ /4\d{2}/
              error = BW::JSON.parse error
              message = error["errors"] = error["errors"].map { |e|
                if e.kind_of?(String)
                  e
                else
                  e.join(" ")
                end
              }.join(", ")
              block.call(nil, {"title" => error["message"], "message" => message}) if block
            else
              block.call(nil, {"message" => result.error.localizedDescription}) if block
              # block.call(nil, result.error.localizedDescription) if block
            end
          end
        end
      end
    end
  end
end

7个end连续... ，分多几个方法出来看起来会更优雅些:)