class ROM::Memory::Dataset
In-memory dataset
This class can be used as a base class for other adapters.
@api public
Public Instance Methods
Delete tuples from a dataset
@param [Hash] tuple A new tuple for deletion
@return [Dataset]
@api public
# File lib/rom/memory/dataset.rb, line 110 def delete(tuple) data.delete(tuple) self end
Insert tuple into a dataset
@param [Hash] tuple A new tuple for insertion
@api public
@return [Dataset]
# File lib/rom/memory/dataset.rb, line 97 def insert(tuple) data << tuple self end
Join with other datasets
@param [Array<Dataset>] args A list of dataset to join with
@return [Dataset]
@api public
# File lib/rom/memory/dataset.rb, line 22 def join(*args) left, right = args.size > 1 ? args : [self, args.first] join_map = left.each_with_object({}) { |tuple, h| others = right.to_a.find_all { |t| (tuple.to_a & t.to_a).any? } (h[tuple] ||= []).concat(others) } tuples = left.flat_map { |tuple| join_map[tuple].map { |other| tuple.merge(other) } } self.class.new(tuples, **options) end
Sort a dataset
@param [Array<Symbol>] fields
Names of fields to order tuples by
@option [Boolean] :nils_first (false)
Whether `nil` values should be placed before others
@return [Dataset]
@api public
# File lib/rom/memory/dataset.rb, line 80 def order(*fields) nils_first = fields.pop[:nils_first] if fields.last.is_a?(Hash) sort do |a, b| fields # finds the first difference between selected fields of tuples .map { |n| __compare__ a[n], b[n], nils_first } .detect(-> { 0 }) { |r| r != 0 } end end
Project a dataset
@param [Array<Symbol>] names A list of attribute names
@return [Dataset]
@api public
# File lib/rom/memory/dataset.rb, line 65 def project(*names) map { |tuple| tuple.select { |key| names.include?(key) } } end
Restrict a dataset
@param [Hash] criteria A hash with conditions
@return [Dataset]
@api public
# File lib/rom/memory/dataset.rb, line 44 def restrict(criteria = nil) return find_all { |tuple| yield(tuple) } unless criteria find_all do |tuple| criteria.all? do |k, v| case v when Array then v.include?(tuple[k]) when Regexp then tuple[k].match(v) else tuple[k].eql?(v) end end end end
Private Instance Methods
Compares two values, that are either comparable, or can be nils
@api private
# File lib/rom/memory/dataset.rb, line 120 def __compare__(a, b, nils_first) return a <=> b unless a.nil? ^ b.nil? nils_first ^ b.nil? ? -1 : 1 end