Module: Farce::Abstract::Value Abstract

Included in:
Atom, Counter, Flag, Lazy, Envelope, WeakValue
Defined in:
lib/farce/abstract/value.rb,
lib/farce/integrations/active_support/blank.rb

Overview

This module is abstract.

Mixin to indicate #value can safely be called on an object.

ActiveSupport Integration collapse

Instance Method Summary collapse

Instance Method Details

#blank? ⇒ Boolean

Note:

This methods is only available if ActiveSupport has been loaded.

Returns true if the value is blank, false otherwise.

Returns:

  • (Boolean) —

    true if the value is blank, false otherwise.



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# File 'lib/farce/integrations/active_support/blank.rb', line 40

def blank? = value.blank?

#unwrap(default = nil) ⇒ BasicObject #unwrap {|value| ... } ⇒ BasicObject

Unwraps nested Farce::Abstract::Value objects to get the underlying value.

Examples:

Nested unwrapping

MyValue = Data.define(:value) { include Farce::Abstract::Value }
inner   = MyValue.new(42)
outer   = MyValue.new(inner)
outer.unwrap # => 42

Cycle detection

MyValue = Struct.new(:name, :value) { include Farce::Abstract::Value }

a = MyValue.new("A")
b = MyValue.new("B", a)
c = MyValue.new("C", a)
a.value = b

c.unwrap # => nil
c.unwrap("default") # => "default"

# RuntimeError: cycle detected starting at A
c.unwrap { raise "cycle detected starting at #{value.name}" }

Overloads:

  • #unwrap(default = nil) ⇒ BasicObject

    Parameters:

    • default (BasicObject) (defaults to: nil) —

      The value to return if a cycle is detected.

  • #unwrap {|value| ... } ⇒ BasicObject

    Yields:

    • (value) —

      Block to call if a cycle is detected.

    Yield Parameters:

    • value (Value) —

      The value that has been determined to be the start of the cycle.

    Yield Returns:

    • (BasicObject) —

      The value to return if a cycle is detected

Returns:

  • (BasicObject) —

    The underlying value of the object, or a default value based on the argument or block.



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# File 'lib/farce/abstract/value.rb', line 51

def unwrap(default = nil)
  value = value()
  return value unless value.is_a?(Value)

  seen = ::Set.new.compare_by_identity
  seen << self

  while value.is_a?(Value)
    return block_given? ? yield(value) : default if seen.include?(value)
    seen << value
    value = value.value
  end

  value
end

#value ⇒ BasicObject

This method is abstract.

Can be called multiple times without argument. Some subclasses may allow optional arguments, especially a timeout keyword argument. This method may block.

Returns:

  • (BasicObject) —

    The underlying value of the object.



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# File 'lib/farce/abstract/value.rb', line 17

module Value
  Internal::Atom.include(self)

  # Unwraps nested {Value} objects to get the underlying value.
  #
  # @example Nested unwrapping
  #   MyValue = Data.define(:value) { include Farce::Abstract::Value }
  #   inner   = MyValue.new(42)
  #   outer   = MyValue.new(inner)
  #   outer.unwrap # => 42
  #
  # @example Cycle detection
  #   MyValue = Struct.new(:name, :value) { include Farce::Abstract::Value }
  #
  #   a = MyValue.new("A")
  #   b = MyValue.new("B", a)
  #   c = MyValue.new("C", a)
  #   a.value = b
  #
  #   c.unwrap # => nil
  #   c.unwrap("default") # => "default"
  #
  #   # RuntimeError: cycle detected starting at A
  #   c.unwrap { raise "cycle detected starting at #{value.name}" }
  #
  # @overload unwrap(default = nil)
  #   @param [BasicObject] default The value to return if a cycle is detected.
  #
  # @overload unwrap
  #   @yield [value] Block to call if a cycle is detected.
  #   @yieldparam [Value] value The value that has been determined to be the start of the cycle.
  #   @yieldreturn [BasicObject] The value to return if a cycle is detected
  #
  # @return [BasicObject] The underlying value of the object, or a default value based on the argument or block.
  def unwrap(default = nil)
    value = value()
    return value unless value.is_a?(Value)

    seen = ::Set.new.compare_by_identity
    seen << self

    while value.is_a?(Value)
      return block_given? ? yield(value) : default if seen.include?(value)
      seen << value
      value = value.value
    end

    value
  end
end