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A XML parameters parser for Action Pack (removed from core in Rails 4.0)


Include this gem into your Gemfile:

gem 'actionpack-xml_parser'

Then, add ActionDispatch::XmlParamsParser middleware after ActionDispatch::ParamsParser in config/application.rb:

config.middleware.insert_after ActionDispatch::ParamsParser, ActionDispatch::XmlParamsParser

You may need to require the ActionDispatch::XmlParamsParser manually. Add the following in your config/application.rb:

require 'action_dispatch/xml_params_parser'

Parameters parsing rules

The parameters parsing is handled by ActiveSupport::XMLConverter so there may be specific features and subtle differences depending on the chosen XML backend.


Basically, each node represents a key. With the following XML:


The resulting parameters will be:

{"person" => {"name" => "David"}}

File attachment

You can specify the type attribute of a node to attach files:

  <avatar type="file" name="me.jpg" content_type="image/jpg"><!-- File content --></avatar>

The resulting parameters will include a StringIO object with the given content, name and content type set accordingly:

{"person" => {"avatar" => #<StringIO:...>}}


There are several ways to pass an array. You can either specify multiple nodes with the same name:

  <address city="Chicago"/>
  <address city="Ottawa"/>

The resulting parameters will be:

{"person" => {"address" => [{"city" => "Chicago"}, {"city" => "Ottawa"}]}}

You can also specify the type attribute of a node and nest child nodes inside:

  <addresses type="array">
    <address city="Melbourne"/>
    <address city="Paris"/>

will result in:

{"person" => {"addresses" => [{"city" => "Melbourne"}, {"city" => "Paris"}]}}
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