Module: UniqueBy::Generator

Defined in:
lib/unique_by.rb

Instance Method Summary collapse

Instance Method Details

#unique_by(*group_block_names, total: nil, bits: nil, &group_block) ⇒ Object

For a primary_key ‘id’, generates:

::unique_id_from(group, id) => unique_id
::id_from(unique_id) => id
::id_group_from(unique_id) => group
#id_group => group
#unique_id => unique_id
::find_by_unique_id(unique_id) => find_by_id(id_from(unique_id))
::find_by_unique_id!(unique_id) => find_by_id!(id_from(unique_id))

Raises:

  • (ArgumentError) 


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# File 'lib/unique_by.rb', line 13

def unique_by(*group_block_names, total: nil, bits: nil, &group_block)
  bits, total = Array(bits), Array(total)

  raise ArgumentError, "must pass either bits or total to #unique_by" \
    unless bits.any? or total.any?
  raise ArgumentError, "both bits (#{bits.inspect}) and total (#{total.inspect}) passed to #unique_by" \
    if bits.any? and total.any?
  raise ArgumentError, "must pass a group generator block" \
    unless group_block_names.any? or block_given?
  raise ArgumentError, "amount of group names (#{group_block_names.length}) doesn't match amount of bits/total (#{bits.length + total.length})" \
    if group_block_names.any? and not block_given? and group_block_names.length != bits.length + total.length

  bits = total.map { |t| Math.log2(t).ceil } if bits.empty?
  total = bits.map { |b| 2 ** b }

  pk = primary_key # converting to a local variable

  define_singleton_method :"unique_#{pk}_from" do |group_value, value|
    (value.to_i << bits.sum) + group_value.to_i
  end

  define_singleton_method :"#{pk}_from" do |value|
    value.to_i >> bits
  end

  define_singleton_method :"#{pk}_group_from" do |value|
    value.to_i & ((2 ** bits.sum) - 1)
  end

  define_method :"#{pk}_group" do
    group_values = group_block_names.map { |group_block_name| send(group_block_name) }
    group_values.push(*Array(instance_eval(group_block))) if group_block
    raise "amount of groups (#{group_values.length}) doesn't match amount of bits/total (#{bits.length})" if group_values.length != bits.length
    group_values.each_with_index.reduce(0) do |group, (group_value, i)|
      raise "group must implement #to_i, #{group_value} given" \
        unless group_value.respond_to?(&:to_i)
      (group << bits[i]) + (group_value.to_i % total[i])
    end
  end

  define_method :"unique_#{pk}" do
    primary_key = send(pk)
    raise "#{pk} must implement #to_i, #{primary_key.inspect} given" \
      unless primary_key.respond_to?(:to_i)
    self.class.send(:"unique_#{pk}_from", send(:"#{pk}_group"), primary_key.to_i)
  end

  define_singleton_method :"find_by_unique_#{pk}" do |value|
    send(:"find_by_#{pk}". send(:"#{pk}_from", value))
  end

  define_singleton_method :"find_by_unique_#{pk}!" do |value|
    send(:"find_by_#{pk}!". send(:"#{pk}_from", value))
  end
end