Module: Naught::Conversions

Defined in:
lib/naught/conversions.rb

Overview

Helper conversion API available on generated null classes

This module is designed to be configured per null class via Conversions.configure. Each generated null class gets its own configured version of these conversion functions.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.configure(mod, null_class:, null_equivs:) ⇒ void

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

This method returns an undefined value.

Configure a Conversions module for a specific null class

Parameters:

  • mod (Module) —

    module to configure

  • null_class (Class) —

    the generated null class

  • null_equivs (Array) —

    values treated as null-equivalent



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# File 'lib/naught/conversions.rb', line 22

def configure(mod, null_class:, null_equivs:)
  mod.define_method(:__null_class__) { null_class }
  mod.define_method(:__null_equivs__) { null_equivs }
  mod.send(:private, :__null_class__, :__null_equivs__)
end

Instance Method Details

#Actual(object = nil) ⇒ Object?

Return nil for null objects, otherwise return the value

Examples:

Actual(null)     #=> nil
Actual("hello")  #=> "hello"

Parameters:

  • object (Object) (defaults to: nil) —

    candidate object

Yield Returns:

  • (Object) —

    optional lazy value

Returns:

  • (Object, nil) —

    actual value or nil



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# File 'lib/naught/conversions.rb', line 92

def Actual(object = nil)
  object = yield if block_given?
  null_object?(object) ? nil : object
end

#Just(object = nil) ⇒ Object

Return the value if not null-equivalent, otherwise raise

Examples:

Just("hello")  #=> "hello"
Just(nil)      # raises ArgumentError

Parameters:

  • object (Object) (defaults to: nil) —

    candidate object

Yield Returns:

  • (Object) —

    optional lazy value

Returns:

  • (Object) —

    original value

Raises:

  • (ArgumentError) —

    if value is null-equivalent



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# File 'lib/naught/conversions.rb', line 74

def Just(object = nil)
  object = yield if block_given?
  if null_object?(object) || null_equivalent?(object)
    raise ArgumentError, "Just() requires a non-null value, got: #{object.inspect}"
  end

  object
end

#Maybe(object = nil) ⇒ Object

Return a null object for null-equivalent values, otherwise the value

Examples:

Maybe(nil)        #=> <null>
Maybe("hello")    #=> "hello"

Parameters:

  • object (Object) (defaults to: nil) —

    candidate object

Yield Returns:

  • (Object) —

    optional lazy value

Returns:

  • (Object) —

    null object or original value



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# File 'lib/naught/conversions.rb', line 56

def Maybe(object = nil)
  object = yield if block_given?
  return object if null_object?(object)
  return make_null(1) if null_equivalent?(object)

  object
end

#Null(object = NOTHING_PASSED) ⇒ Object

Return a null object for object if it is null-equivalent

Examples:

include MyNullObject::Conversions
Null()       #=> <null>
Null(nil)    #=> <null>

Parameters:

  • object (Object) (defaults to: NOTHING_PASSED) —

    candidate object

Returns:

  • (Object) —

    a null object

Raises:

  • (ArgumentError) —

    if object is not null-equivalent



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# File 'lib/naught/conversions.rb', line 39

def Null(object = NOTHING_PASSED)
  return object if null_object?(object)
  return make_null(1) if null_equivalent?(object, include_nothing: true)

  raise ArgumentError, "Null() requires a null-equivalent value, " \
                       "got #{object.class}: #{object.inspect}"
end