Class: ArOuterJoins::JoinBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/ar_outer_joins/join_builder.rb

Defined Under Namespace

Classes: OuterJoinError

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(association) ⇒ JoinBuilder

Returns a new instance of JoinBuilder.



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# File 'lib/ar_outer_joins/join_builder.rb', line 7

def initialize(association)
  @association = association
end

Instance Attribute Details

#association ⇒ Object (readonly)

Returns the value of attribute association.



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# File 'lib/ar_outer_joins/join_builder.rb', line 5

def association
  @association
end

Instance Method Details

#build ⇒ Object 



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# File 'lib/ar_outer_joins/join_builder.rb', line 11

def build
  if association.is_a? ActiveRecord::Reflection::ThroughReflection
    [
      JoinBuilder.new(association.through_reflection).build,
      JoinBuilder.new(association.source_reflection).build
    ].flatten
  else
    table = association.active_record.arel_table
    primary_key = association.active_record.primary_key
    joined_table = association.klass.arel_table

    case association.macro
    when :belongs_to
      on = Arel::Nodes::On.new(table[association.foreign_key].eq(joined_table[primary_key]))
      [Arel::Nodes::OuterJoin.new(joined_table, on)]
    when :has_and_belongs_to_many
      join_model_table = if association.respond_to?(:join_table)
          Arel::Table.new(association.join_table)
        else
          Arel::Table.new(association.options[:join_table])
        end
      joined_primary_key = association.klass.primary_key

      on1 = Arel::Nodes::On.new(join_model_table[association.foreign_key].eq(table[primary_key]))
      on2 = Arel::Nodes::On.new(join_model_table[association.association_foreign_key].eq(joined_table[joined_primary_key]))

      [Arel::Nodes::OuterJoin.new(join_model_table, on1), Arel::Nodes::OuterJoin.new(joined_table, on2)]
    when :has_many, :has_one
      on = Arel::Nodes::On.new(joined_table[association.foreign_key].eq(table[primary_key]))
      [Arel::Nodes::OuterJoin.new(joined_table, on)]
    else
      raise OuterJoinError, "don't know what to do with #{association.macro} association"
    end
  end
end