Class: Mongoid::Criteria

Inherits:
Object show all
Defined in:
lib/frecon/mongoid/criteria.rb

Overview

Public: A monkey-patch for the Mongoid::Criteria class which introduces a #psv_filter method.

Instance Method Summary collapse

Instance Method Details

#psv_filter(psv_parameters = {}) ⇒ Object

Public: Filter by given PSV parameters.

PSV is an introduced system that can be used within query strings to narrow a query. Since HTTP query strings can use ‘+’ to act as spaces within a key-value pair, one can use these pluses to define nested query parameters when querying the database as in an indexing or showing request.

psv_parameters - A Hash of PSV strings to comparison values.

Examples

Record.all.psv_filter({'participation robot team number' => '2503'})
=> #<Mongoid::Criteria ...>

# Since each instance of Record has a :team shortcut method,
# we can just filter it like so.
Record.all.psv_filter({'team number' => '2503'})
=> #<Mongoid::Criteria ...>

Returns a filtered version of self.



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# File 'lib/frecon/mongoid/criteria.rb', line 39

def psv_filter(psv_parameters = {})
	collection = self

	# Iterate through the Hash of query Strings to values, filtering using
	# each pairing where the key is the query specifier and the value is the
	# value that the last word in the query specifier is equal to.  For
	# multiple key-value pairs, just keep adding specifiers to the chain.
	psv_parameters.each do |psv_string, comparison_value|
		# Split the query String, and convert each subsequent String
		# to a symbol.  Then, reverse the array to make it easy to perform
		# an inside-out operation.
		psv_keys = psv_string.split(/\W/).map do |psv_key|
			psv_key.to_sym
		end.reverse

		# Get the final key in the query string.
		comparison_key = psv_keys.shift

		# Create a comparison hash to be used to compare <attribute> to
		# <expected value>.
		if comparison_value.length == 0 || comparison_value == '__nil__'
			comparison_hash = {comparison_key => nil}
		else
			comparison_hash = {comparison_key => comparison_value}
		end

		# Each of the subsequent keys should be a model name.  Generate a string
		# corresponding to the '<model>' + '_id' for use as the comparison key,
		# and find the model class by generating a constant.
		#
		# Then, nest a comparison around the current comparison hash.
		psv_keys.each do |model|
			model_id = (model.to_s + '_id').to_sym
			model_class = ('FReCon::' + model.to_s.capitalize).constantize

			comparison_hash = {model_id => model_class.in(comparison_hash).map(&:id)}
		end

		# Finally, complete this nested comparison.
		collection = collection.in(comparison_hash)
	end

	# Return the fully-filtered collection.
	collection
end