diff options
Diffstat (limited to 'activerecord/lib/active_record/associations/through_association.rb')
| -rw-r--r-- | activerecord/lib/active_record/associations/through_association.rb | 281 |
1 files changed, 281 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb new file mode 100644 index 0000000000..ed24373cba --- /dev/null +++ b/activerecord/lib/active_record/associations/through_association.rb @@ -0,0 +1,281 @@ +require 'enumerator' + +module ActiveRecord + # = Active Record Through Association + module Associations + module ThroughAssociation #:nodoc: + + delegate :source_options, :through_options, :source_reflection, :through_reflection, + :through_reflection_chain, :through_conditions, :to => :reflection + + protected + + def target_scope + super.merge(through_reflection.klass.scoped) + end + + def association_scope + scope = super.joins(construct_joins) + scope = scope.where(reflection_conditions(0)) + + unless options[:include] + scope = scope.includes(source_options[:include]) + end + + scope + end + + private + + # This scope affects the creation of the associated records (not the join records). At the + # moment we only support creating on a :through association when the source reflection is a + # belongs_to. Thus it's not necessary to set a foreign key on the associated record(s), so + # this scope has can legitimately be empty. + def creation_attributes + { } + end + + # TODO: Needed? + def aliased_through_table + name = through_reflection.table_name + + reflection.table_name == name ? + through_reflection.klass.arel_table.alias(name + "_join") : + through_reflection.klass.arel_table + end + + def construct_owner_conditions + reflection = through_reflection_chain.last + + if reflection.macro == :has_and_belongs_to_many + table = tables[reflection].first + else + table = Array.wrap(tables[reflection]).first + end + + super(table, reflection) + end + + def construct_joins + joins, right_index = [], 1 + + # Iterate over each pair in the through reflection chain, joining them together + through_reflection_chain.each_cons(2) do |left, right| + left_table, right_table = tables[left], tables[right] + + if left.source_reflection.nil? + case left.macro + when :belongs_to + joins << inner_join( + right_table, + left_table[left.association_primary_key], + right_table[left.foreign_key], + reflection_conditions(right_index) + ) + when :has_many, :has_one + joins << inner_join( + right_table, + left_table[left.foreign_key], + right_table[right.association_primary_key], + polymorphic_conditions(left, left), + reflection_conditions(right_index) + ) + when :has_and_belongs_to_many + joins << inner_join( + right_table, + left_table.first[left.foreign_key], + right_table[right.klass.primary_key], + reflection_conditions(right_index) + ) + end + else + case left.source_reflection.macro + when :belongs_to + joins << inner_join( + right_table, + left_table[left.association_primary_key], + right_table[left.foreign_key], + source_type_conditions(left), + reflection_conditions(right_index) + ) + when :has_many, :has_one + if right.macro == :has_and_belongs_to_many + join_table, right_table = tables[right] + end + + joins << inner_join( + right_table, + left_table[left.foreign_key], + right_table[left.source_reflection.active_record_primary_key], + polymorphic_conditions(left, left.source_reflection), + reflection_conditions(right_index) + ) + + if right.macro == :has_and_belongs_to_many + joins << inner_join( + join_table, + right_table[right.klass.primary_key], + join_table[right.association_foreign_key] + ) + end + when :has_and_belongs_to_many + join_table, left_table = tables[left] + + joins << inner_join( + join_table, + left_table[left.klass.primary_key], + join_table[left.association_foreign_key] + ) + + joins << inner_join( + right_table, + join_table[left.foreign_key], + right_table[right.klass.primary_key], + reflection_conditions(right_index) + ) + end + end + + right_index += 1 + end + + joins + end + + # Construct attributes for :through pointing to owner and associate. This is used by the + # methods which create and delete records on the association. + # + # We only support indirectly modifying through associations which has a belongs_to source. + # This is the "has_many :tags, :through => :taggings" situation, where the join model + # typically has a belongs_to on both side. In other words, associations which could also + # be represented as has_and_belongs_to_many associations. + # + # We do not support creating/deleting records on the association where the source has + # some other type, because this opens up a whole can of worms, and in basically any + # situation it is more natural for the user to just create or modify their join records + # directly as required. + def construct_join_attributes(*records) + if source_reflection.macro != :belongs_to + raise HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(owner, reflection) + end + + join_attributes = { + source_reflection.foreign_key => + records.map { |record| + record.send(source_reflection.association_primary_key) + } + } + + if options[:source_type] + join_attributes[source_reflection.foreign_type] = + records.map { |record| record.class.base_class.name } + end + + if records.count == 1 + Hash[join_attributes.map { |k, v| [k, v.first] }] + else + join_attributes + end + end + + def alias_tracker + @alias_tracker ||= AliasTracker.new + end + + # TODO: It is decidedly icky to have an array for habtm entries, and no array for others + def tables + @tables ||= begin + Hash[ + through_reflection_chain.map do |reflection| + table = alias_tracker.aliased_table_for( + reflection.table_name, + table_alias_for(reflection, reflection != self.reflection) + ) + + if reflection.macro == :has_and_belongs_to_many || + (reflection.source_reflection && + reflection.source_reflection.macro == :has_and_belongs_to_many) + + join_table = alias_tracker.aliased_table_for( + (reflection.source_reflection || reflection).options[:join_table], + table_alias_for(reflection, true) + ) + + [reflection, [join_table, table]] + else + [reflection, table] + end + end + ] + end + end + + def table_alias_for(reflection, join = false) + name = alias_tracker.pluralize(reflection.name) + name << "_#{self.reflection.name}" + name << "_join" if join + name + end + + def inner_join(table, left_column, right_column, *conditions) + conditions << left_column.eq(right_column) + + table.create_join( + table, + table.create_on(table.create_and(conditions.flatten.compact))) + end + + def reflection_conditions(index) + reflection = through_reflection_chain[index] + conditions = through_conditions[index].dup + + # TODO: maybe this should go in Reflection#through_conditions directly? + unless reflection.klass.descends_from_active_record? + conditions << reflection.klass.send(:type_condition) + end + + unless conditions.empty? + conditions.map! do |condition| + condition = reflection.klass.send(:sanitize_sql, interpolate(condition), reflection.table_name) + condition = Arel.sql(condition) unless condition.is_a?(Arel::Node) + condition + end + + Arel::Nodes::And.new(conditions) + end + end + + def polymorphic_conditions(reflection, polymorphic_reflection) + if polymorphic_reflection.options[:as] + tables[reflection][polymorphic_reflection.type]. + eq(polymorphic_reflection.active_record.base_class.name) + end + end + + def source_type_conditions(reflection) + if reflection.options[:source_type] + tables[reflection.through_reflection][reflection.foreign_type]. + eq(reflection.options[:source_type]) + end + end + + # TODO: Think about this in the context of nested associations + def stale_state + if through_reflection.macro == :belongs_to + owner[through_reflection.foreign_key].to_s + end + end + + def foreign_key_present? + through_reflection.macro == :belongs_to && + !owner[through_reflection.foreign_key].nil? + end + + def ensure_not_nested + if reflection.nested? + raise HasManyThroughNestedAssociationsAreReadonly.new(owner, reflection) + end + end + end + end +end |