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YAML(tm) (rhymes with 'camel') is a straightforward machine parsable data serialization format designed for human readability and interaction with scripting languages such as Perl and Python. YAML is optimized for data serialization, formatted dumping, configuration files, log files, Internet messaging and filtering. This specification describes the YAML information model and serialization format. Together with the Unicode standard for characters, it provides all the information necessary to understand YAML Version 1.0 and construct computer programs to process it.
See yaml.org/ for more information. For a quick tutorial, please visit YAML In Five Minutes (yaml.kwiki.org/?YamlInFiveMinutes).
The YAML 1.0 specification outlines four stages of YAML loading and dumping. This library honors all four of those stages, although data is really only available to you in three stages.
The four stages are: native, representation, serialization, and presentation.
The native stage refers to data which has been loaded completely into
Ruby's own types. (See YAML::load
.)
The representation stage means data which has been composed into
YAML::BaseNode
objects. In this stage, the document is
available as a tree of node objects. You can perform YPath queries and transformations at this level.
(See YAML::parse
.)
The serialization stage happens inside the parser. The YAML parser used in Ruby is called Syck. Serialized nodes are available in the extension as SyckNode structs.
The presentation stage is the YAML document itself. This is accessible to
you as a string. (See YAML::dump
.)
For more information about the various information models, see Chapter 3 of the YAML 1.0 Specification (yaml.org/spec/#id2491269).
The YAML module provides quick access to the most common loading (YAML::load) and dumping (YAML::dump) tasks. This module also provides an API for registering global types (YAML::add_domain_type).
A simple round-trip (load and dump) of an object.
require "yaml" test_obj = ["dogs", "cats", "badgers"] yaml_obj = YAML::dump( test_obj ) # -> --- - dogs - cats - badgers ruby_obj = YAML::load( yaml_obj ) # => ["dogs", "cats", "badgers"] ruby_obj == test_obj # => true
To register your custom types with the global resolver, use
add_domain_type
.
YAML::add_domain_type( "your-site.com,2004", "widget" ) do |type, val| Widget.new( val ) end
YAML::BaseNode class
Constants used throughout the library
Handle Unicode-to-Internal conversion
Error messages and exception class
YAML::Loader class .. type handling ..
$Id: tag.rb 27365 2010-04-16 20:31:59Z tenderlove $
why the lucky stiff
Classes required by the full core typeset
Default settings
Error messages
Constants
Parser tokens
Add a transfer method for a builtin type
# File syck/lib/syck.rb, line 310 def self.add_builtin_type( type_tag, &transfer_proc ) resolver.add_type( "tag:yaml.org,2002:#{ type_tag }", transfer_proc ) end
Add a global handler for a YAML domain type.
# File syck/lib/syck.rb, line 303 def self.add_domain_type( domain, type_tag, &transfer_proc ) resolver.add_type( "tag:#{ domain }:#{ type_tag }", transfer_proc ) end
Add a private document type
# File syck/lib/syck.rb, line 325 def self.add_private_type( type_re, &transfer_proc ) warn "#{caller[0]}: YAML.add_private_type is deprecated, use add_domain_type" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) resolver.add_type( "x-private:" + type_re, transfer_proc ) end
Add a transfer method for a builtin type
# File syck/lib/syck.rb, line 317 def self.add_ruby_type( type_tag, &transfer_proc ) warn "#{caller[0]}: YAML.add_ruby_type is deprecated, use add_domain_type" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) resolver.add_type( "tag:ruby.yaml.org,2002:#{ type_tag }", transfer_proc ) end
Detect typing of a string
# File syck/lib/syck.rb, line 333 def self.detect_implicit( val ) warn "#{caller[0]}: YAML.detect_implicit is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) resolver.detect_implicit( val ) end
Converts obj to YAML and writes the YAML result to io.
File.open( 'animals.yaml', 'w' ) do |out| YAML.dump( ['badger', 'elephant', 'tiger'], out ) end
If no io is provided, a string containing the dumped YAML is returned.
YAML.dump( :locked ) #=> "--- :locked"
# File syck/lib/syck.rb, line 117 def self.dump( obj, io = nil ) obj.to_yaml( io || io2 = StringIO.new ) io || ( io2.rewind; io2.read ) end
Returns a YAML stream containing each of the items in objs
,
each having their own document.
YAML.dump_stream( 0, [], {} ) #=> --- 0 --- [] --- {}
# File syck/lib/syck.rb, line 292 def self.dump_stream( *objs ) d = Stream.new objs.each do |doc| d.add( doc ) end d.emit end
Calls block with each consecutive document in the YAML stream contained in io.
File.open( 'many-docs.yaml' ) do |yf| YAML.each_document( yf ) do |ydoc| ## ydoc contains the single object ## from the YAML document end end
# File syck/lib/syck.rb, line 217 def self.each_document( io, &block ) warn "#{caller[0]}: YAML.each_document is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) yp = parser.load_documents( io, &block ) end
Calls block with a tree of YAML::BaseNodes
, one tree
for each consecutive document in the YAML stream contained in io.
File.open( 'many-docs.yaml' ) do |yf| YAML.each_node( yf ) do |ydoc| ## ydoc contains a tree of nodes ## from the YAML document end end
# File syck/lib/syck.rb, line 248 def self.each_node( io, &doc_proc ) warn "#{caller[0]}: YAML.each_node is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) yp = generic_parser.load_documents( io, &doc_proc ) end
Returns a new default emitter
# File syck/lib/syck.rb, line 99 def self.emitter warn "#{caller[0]}: YAML.emitter is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) Emitter.new.set_resolver( self.resolver ) end
Escape the string, condensing common escapes
# File syck/lib/syck/encoding.rb, line 10 def self.escape( value, skip = "" ) warn "#{caller[0]}: YAML.escape is deprecated" if $VERBOSE value.gsub( /\\/, "\\\\\\" ). gsub( /"/, "\\\"" ). gsub( /([\x00-\x1f])/ ) do skip[$&] || ESCAPES[ $&.unpack("C")[0] ] end end
Returns a new generic parser
# File syck/lib/syck.rb, line 87 def self.generic_parser warn "#{caller[0]}: YAML.generic_parser is deprecated, switch to psych" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) Parser.new.set_resolver( GenericResolver ) end
Load a document from the current io stream.
File.open( 'animals.yaml' ) { |yf| YAML::load( yf ) } #=> ['badger', 'elephant', 'tiger']
Can also load from a string.
YAML.load( "--- :locked" ) #=> :locked
# File syck/lib/syck.rb, line 133 def self.load( io ) yp = parser.load( io ) end
Calls block with each consecutive document in the YAML stream contained in io.
File.open( 'many-docs.yaml' ) do |yf| YAML.load_documents( yf ) do |ydoc| ## ydoc contains the single object ## from the YAML document end end
# File syck/lib/syck.rb, line 233 def self.load_documents( io, &doc_proc ) yp = parser.load_documents( io, &doc_proc ) end
Load a document from the file located at filepath.
YAML.load_file( 'animals.yaml' ) #=> ['badger', 'elephant', 'tiger']
# File syck/lib/syck.rb, line 143 def self.load_file( filepath ) File.open( filepath ) do |f| load( f ) end end
Loads all documents from the current io stream, returning a
YAML::Stream
object containing all loaded documents.
# File syck/lib/syck.rb, line 274 def self.load_stream( io ) d = nil parser.load_documents( io ) do |doc| d = Stream.new if not d d.add( doc ) end return d end
Class method for creating streams
# File syck/lib/syck/stringio.rb, line 57 def Syck.make_stream( io ) if String === io io = StringIO.new( io ) elsif not IO === io raise Syck::Error, "YAML stream must be an IO or String object." end if Syck::unicode def io.readline Syck.utf_to_internal( readline( @ln_sep ), @utf_encoding ) end def io.check_unicode @utf_encoding = Syck.sniff_encoding( read( 4 ) ) @ln_sep = Syck.enc_separator( @utf_encoding ) seek( -4, IO::SEEK_CUR ) end def io.utf_encoding @utf_encoding end io.check_unicode else def io.utf_encoding :None end end io end
Allocate blank object
# File syck/lib/syck.rb, line 376 def self.object_maker( obj_class, val ) warn "#{caller[0]}: YAML.object_maker is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) if Hash === val o = obj_class.allocate val.each_pair { |k,v| o.instance_variable_set("@#{k}", v) } o else raise Error, "Invalid object explicitly tagged !ruby/Object: " + val.inspect end end
Parse the first document from the current io stream
File.open( 'animals.yaml' ) { |yf| YAML::load( yf ) } #=> #<YAML::Syck::Node:0x82ccce0 @kind=:seq, @value= [#<YAML::Syck::Node:0x82ccd94 @kind=:scalar, @type_id="str", @value="badger">, #<YAML::Syck::Node:0x82ccd58 @kind=:scalar, @type_id="str", @value="elephant">, #<YAML::Syck::Node:0x82ccd1c @kind=:scalar, @type_id="str", @value="tiger">]>
Can also load from a string.
YAML.parse( "--- :locked" ) #=> #<YAML::Syck::Node:0x82edddc @type_id="tag:ruby.yaml.org,2002:sym", @value=":locked", @kind=:scalar>
# File syck/lib/syck.rb, line 176 def self.parse( io ) yp = generic_parser.load( io ) end
Calls block with a tree of YAML::BaseNodes
, one tree
for each consecutive document in the YAML stream contained in io.
File.open( 'many-docs.yaml' ) do |yf| YAML.parse_documents( yf ) do |ydoc| ## ydoc contains a tree of nodes ## from the YAML document end end
# File syck/lib/syck.rb, line 264 def self.parse_documents( io, &doc_proc ) warn "#{caller[0]}: YAML.parse_documents is deprecated, use load_stream" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) self.each_node( io, &doc_proc ) end
Parse a document from the file located at filepath.
YAML.parse_file( 'animals.yaml' ) #=> #<YAML::Syck::Node:0x82ccce0 @kind=:seq, @value= [#<YAML::Syck::Node:0x82ccd94 @kind=:scalar, @type_id="str", @value="badger">, #<YAML::Syck::Node:0x82ccd58 @kind=:scalar, @type_id="str", @value="elephant">, #<YAML::Syck::Node:0x82ccd1c @kind=:scalar, @type_id="str", @value="tiger">]>
# File syck/lib/syck.rb, line 200 def self.parse_file( filepath ) File.open( filepath ) do |f| parse( f ) end end
Returns a new default parser
# File syck/lib/syck.rb, line 84 def self.parser; Parser.new.set_resolver( self.resolver ); end
Allocate an Emitter if needed
# File syck/lib/syck.rb, line 392 def self.quick_emit( oid, opts = {}, &e ) warn "#{caller[0]}: YAML.quick_emit is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) out = if opts.is_a? Emitter opts else emitter.reset( opts ) end out.emit( oid, &e ) end
Method to extract colon-seperated type and class, returning the type and the constant of the class
# File syck/lib/syck.rb, line 366 def self.read_type_class( type, obj_class ) warn "#{caller[0]}: YAML.read_type_class is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) scheme, domain, type, tclass = type.split( ':', 4 ) tclass.split( "::" ).each { |c| obj_class = obj_class.const_get( c ) } if tclass return [ type, obj_class ] end
Returns the default resolver
# File syck/lib/syck.rb, line 93 def self.resolver warn "#{caller[0]}: YAML.resolver is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) DefaultResolver end
Associates a taguri tag with a Ruby class cls. The taguri is used to give types to classes when loading YAML. Taguris are of the form:
tag:authorityName,date:specific
The authorityName
is a domain name or email address. The
date
is the date the type was issued in YYYY or YYYY-MM or
YYYY-MM-DD format. The specific
is a name for the type being
added.
For example, built-in YAML types have 'yaml.org' as the
authorityName
and '2002' as the date
.
The specific
is simply the name of the type:
tag:yaml.org,2002:int tag:yaml.org,2002:float tag:yaml.org,2002:timestamp
The domain must be owned by you on the date
declared. If you
don't own any domains on the date you declare the type, you can simply
use an e-mail address.
tag:why@ruby-lang.org,2004:notes/personal
# File syck/lib/syck/tag.rb, line 34 def self.tag_class( tag, cls ) if @@tagged_classes.has_key? tag warn "class #{ @@tagged_classes[tag] } held ownership of the #{ tag } tag" end @@tagged_classes[tag] = cls end
Returns the complete dictionary of taguris, paired with classes. The key for the dictionary is the full taguri. The value for each key is the class constant associated to that taguri.
YAML.tagged_classes["tag:yaml.org,2002:int"] => Integer
# File syck/lib/syck/tag.rb, line 47 def self.tagged_classes @@tagged_classes end
Convert a type_id to a taguri
# File syck/lib/syck.rb, line 341 def self.tagurize( val ) warn "#{caller[0]}: YAML.tagurize is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) resolver.tagurize( val ) end
Apply a transfer method to a Ruby object
# File syck/lib/syck.rb, line 349 def self.transfer( type_id, obj ) warn "#{caller[0]}: YAML.transfer is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) resolver.transfer( tagurize( type_id ), obj ) end
Apply any implicit a node may qualify for
# File syck/lib/syck.rb, line 357 def self.try_implicit( obj ) warn "#{caller[0]}: YAML.try_implicit is deprecated" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__)) transfer( detect_implicit( obj ), obj ) end
Unescape the condenses escapes
# File syck/lib/syck/encoding.rb, line 22 def self.unescape( value ) warn "#{caller[0]}: YAML.unescape is deprecated" if $VERBOSE value.gsub( /\\(?:([nevfbart\\])|0?x([0-9a-fA-F]{2})|u([0-9a-fA-F]{4}))/ ) { if $3 ["#$3".hex ].pack('U*') elsif $2 [$2].pack( "H2" ) else UNESCAPES[$1] end } end