Rails: query parameter vs post parameter

Question

Suppose you have a url

localhost:3000?a=1

and in the request, you also have a post parameter

a=2

What wou

Answer 1

Rails uses Rack::Request for HTTP requests. However, it redefines the Rack params method in ActionDispatch::Http::Parameters (via an alias).

This params method, which returns request parameters, is implemented as:

  # Returns both GET and POST \parameters in a single hash.
  def parameters
    @env["action_dispatch.request.parameters"] ||= begin
      params = request_parameters.merge(query_parameters)
      params.merge!(path_parameters)
      encode_params(params).with_indifferent_access
    end
  end
  alias :params :parameters

Note the aliased parameters method.

Unless redefined, parameters from the query string will overwrite parameters from the POST body.