# module ActionController::ParamsWrapper

Wraps the parameters hash into a nested hash. This will allow clients to submit POST requests without having to specify any root elements.

This functionality is enabled in `config/initializers/wrap_parameters.rb` and can be customized. If you are upgrading to Rails 3.1, this file will need to be created for the functionality to be enabled.

You could also turn it on per controller by setting the format array to a non-empty array:

    class UsersController < ApplicationController
      wrap_parameters :format => [:json, :xml]
    end

If you enable `ParamsWrapper` for `:json` format, instead of having to send JSON parameters like this:

    {"user": {"name": "Konata"}}

You can send parameters like this:

    {"name": "Konata"}

And it will be wrapped into a nested hash with the key name matching the controller’s name. For example, if you’re posting to `UsersController`, your new `params` hash will look like this:

    {"name" => "Konata", "user" => {"name" => "Konata"}}

You can also specify the key in which the parameters should be wrapped to, and also the list of attributes it should wrap by using either `:include` or `:exclude` options like this:

    class UsersController < ApplicationController
      wrap_parameters :person, :include => [:username, :password]
    end

On ActiveRecord models with no `:include` or `:exclude` option set, if attr_accessible is set on that model, it will only wrap the accessible parameters, else it will only wrap the parameters returned by the class method attribute_names.

If you’re going to pass the parameters to an `ActiveModel` object (such as +User.new(params)+), you might consider passing the model class to the method instead. The `ParamsWrapper` will actually try to determine the list of attribute names from the model and only wrap those attributes:

    class UsersController < ApplicationController
      wrap_parameters Person
    end

You still could pass `:include` and `:exclude` to set the list of attributes you want to wrap.

By default, if you don’t specify the key in which the parameters would be wrapped to, `ParamsWrapper` will actually try to determine if there’s a model related to it or not. This controller, for example:

    class Admin::UsersController < ApplicationController
    end

will try to check if +Admin::User+ or `User` model exists, and use it to determine the wrapper key respectively. If both models don’t exist, it will then fallback to use `user` as the key.

### Constants

EXCLUDE_PARAMETERS

### Public Instance Methods

process_action(*args) click to toggle source

Performs parameters wrapping upon the request. Will be called automatically by the metal call stack.

Calls superclass method

    # File lib/action_controller/metal/params_wrapper.rb, line 194
    def process_action(*args)
      if _wrapper_enabled?
        wrapped_hash = _wrap_parameters request.request_parameters
        wrapped_keys = request.request_parameters.keys
        wrapped_filtered_hash = _wrap_parameters request.filtered_parameters.slice(*wrapped_keys)

        # This will make the wrapped hash accessible from controller and view
        request.parameters.merge! wrapped_hash
        request.request_parameters.merge! wrapped_hash

        # This will make the wrapped hash displayed in the log file
        request.filtered_parameters.merge! wrapped_filtered_hash
      end
      super
    end