The Forwardable module provides delegation of specified methods to a designated object, using the methods def_delegator
and def_delegators
.
For example, say you have a class RecordCollection which contains an array @records
. You could provide the lookup method record_number(), which simply calls [] on the @records
array, like this:
require 'forwardable' class RecordCollection attr_accessor :records extend Forwardable def_delegator :@records, :[], :record_number end
We can use the lookup method like so:
r = RecordCollection.new r.records = [4,5,6] r.record_number(0) # => 4
Further, if you wish to provide the methods size, <<, and map, all of which delegate to @records, this is how you can do it:
class RecordCollection # re-open RecordCollection class def_delegators :@records, :size, :<<, :map end r = RecordCollection.new r.records = [1,2,3] r.record_number(0) # => 1 r.size # => 3 r << 4 # => [1, 2, 3, 4] r.map { |x| x * 2 } # => [2, 4, 6, 8]
You can even extend regular objects with Forwardable.
my_hash = Hash.new my_hash.extend Forwardable # prepare object for delegation my_hash.def_delegator "STDOUT", "puts" # add delegation for STDOUT.puts() my_hash.puts "Howdy!"
We want to rely on what has come before obviously, but with delegation we can take just the methods we need and even rename them as appropriate. In many cases this is preferable to inheritance, which gives us the entire old interface, even if much of it isn’t needed.
class Queue extend Forwardable def initialize @q = [ ] # prepare delegate object end # setup preferred interface, enq() and deq()... def_delegator :@q, :push, :enq def_delegator :@q, :shift, :deq # support some general Array methods that fit Queues well def_delegators :@q, :clear, :first, :push, :shift, :size end q = Queue.new q.enq 1, 2, 3, 4, 5 q.push 6 q.shift # => 1 while q.size > 0 puts q.deq end q.enq "Ruby", "Perl", "Python" puts q.first q.clear puts q.first
This should output:
2 3 4 5 6 Ruby nil
Be advised, RDoc
will not detect delegated methods.
forwardable.rb
provides single-method delegation via the def_delegator
and def_delegators
methods. For full-class delegation via DelegateClass, see delegate.rb
.
SingleForwardable
can be used to setup delegation at the object level as well.
printer = String.new printer.extend SingleForwardable # prepare object for delegation printer.def_delegator "STDOUT", "puts" # add delegation for STDOUT.puts() printer.puts "Howdy!"
Also, SingleForwardable
can be used to set up delegation for a Class
or Module
.
class Implementation def self.service puts "serviced!" end end module Facade extend SingleForwardable def_delegator :Implementation, :service end Facade.service #=> serviced!
If you want to use both Forwardable and SingleForwardable
, you can use methods def_instance_delegator and def_single_delegator
, etc.
A module to implement the Linda distributed computing paradigm in Ruby.
See the sample/drb/ directory in the Ruby distribution, from 1.8.2 onwards.
The Math
module contains module functions for basic trigonometric and transcendental functions. See class Float
for a list of constants that define Ruby’s floating point accuracy.
Domains and codomains are given only for real (not complex) numbers.
The top-level class representing any ASN.1 object. When parsed by ASN1.decode
, tagged values are always represented by an instance of ASN1Data
.
ASN1Data
for parsing tagged values When encoding an ASN.1 type it is inherently clear what original type (e.g. INTEGER, OCTET STRING etc.) this value has, regardless of its tagging. But opposed to the time an ASN.1 type is to be encoded, when parsing them it is not possible to deduce the “real type” of tagged values. This is why tagged values are generally parsed into ASN1Data
instances, but with a different outcome for implicit and explicit tagging.
An implicitly 1-tagged INTEGER value will be parsed as an ASN1Data
with
tag equal to 1
tag_class equal to :CONTEXT_SPECIFIC
value equal to a String that carries the raw encoding of the INTEGER.
This implies that a subsequent decoding step is required to completely decode implicitly tagged values.
An explicitly 1-tagged INTEGER value will be parsed as an ASN1Data
with
tag equal to 1
tag_class equal to :CONTEXT_SPECIFIC
value equal to an Array with one single element, an instance of OpenSSL::ASN1::Integer
, i.e. the inner element is the non-tagged primitive value, and the tagging is represented in the outer ASN1Data
int = OpenSSL::ASN1::Integer.new(1, 0, :IMPLICIT) # implicit 0-tagged seq = OpenSSL::ASN1::Sequence.new( [int] ) der = seq.to_der asn1 = OpenSSL::ASN1.decode(der) # pp asn1 => #<OpenSSL::ASN1::Sequence:0x87326e0 # @indefinite_length=false, # @tag=16, # @tag_class=:UNIVERSAL, # @tagging=nil, # @value= # [#<OpenSSL::ASN1::ASN1Data:0x87326f4 # @indefinite_length=false, # @tag=0, # @tag_class=:CONTEXT_SPECIFIC, # @value="\x01">]> raw_int = asn1.value[0] # manually rewrite tag and tag class to make it an UNIVERSAL value raw_int.tag = OpenSSL::ASN1::INTEGER raw_int.tag_class = :UNIVERSAL int2 = OpenSSL::ASN1.decode(raw_int) puts int2.value # => 1
int = OpenSSL::ASN1::Integer.new(1, 0, :EXPLICIT) # explicit 0-tagged seq = OpenSSL::ASN1::Sequence.new( [int] ) der = seq.to_der asn1 = OpenSSL::ASN1.decode(der) # pp asn1 => #<OpenSSL::ASN1::Sequence:0x87326e0 # @indefinite_length=false, # @tag=16, # @tag_class=:UNIVERSAL, # @tagging=nil, # @value= # [#<OpenSSL::ASN1::ASN1Data:0x87326f4 # @indefinite_length=false, # @tag=0, # @tag_class=:CONTEXT_SPECIFIC, # @value= # [#<OpenSSL::ASN1::Integer:0x85bf308 # @indefinite_length=false, # @tag=2, # @tag_class=:UNIVERSAL # @tagging=nil, # @value=1>]>]> int2 = asn1.value[0].value[0] puts int2.value # => 1
Stores multipart form data. FormData
objects are created when WEBrick::HTTPUtils.parse_form_data
is called.
Net::IMAP::BodyTypeAttachment
represents attachment body structures of messages.
Returns the content media type name.
Returns nil
.
Returns a hash that represents parameters.
Returns false.
An InstalledSpecification
represents a gem that is already installed locally.
The StaticSet
is a static set of gem specifications used for testing only. It is available by requiring Gem::TestCase
.
Root of the HTTP status class hierarchy
Common validators of number and nz_number types
Element
used to describe an Atom
date and time in the ISO 8601 format
Examples:
2013-03-04T15:30:02Z
2013-03-04T10:30:02-05:00
Raised by Encoding
and String methods when the source encoding is incompatible with the target encoding.