Class: Psych::Parser

Inherits:
Object show all
Defined in:
lib/psych/parser.rb,
ext/psych/psych_parser.c

Overview

YAML event parser class. This class parses a YAML document and calls events on the handler that is passed to the constructor. The events can be used for things such as constructing a YAML AST or deserializing YAML documents. It can even be fed back to Psych::Emitter to emit the same document that was parsed.

See Psych::Handler for documentation on the events that Psych::Parser emits.

Here is an example that prints out ever scalar found in a YAML document:

# Handler for detecting scalar values
class ScalarHandler < Psych::Handler
  def scalar value, anchor, tag, plain, quoted, style
    puts value
  end
end

parser = Psych::Parser.new(ScalarHandler.new)
parser.parse(yaml_document)

Here is an example that feeds the parser back in to Psych::Emitter. The YAML document is read from STDIN and written back out to STDERR:

parser = Psych::Parser.new(Psych::Emitter.new($stderr))
parser.parse($stdin)

Psych uses Psych::Parser in combination with Psych::TreeBuilder to construct an AST of the parsed YAML document.

Defined Under Namespace

Classes: Mark

Constant Summary collapse

ANY =

Let the parser choose the encoding

Any encoding
UTF8 =

UTF-8 Encoding

INT2NUM(YAML_UTF8_ENCODING)
UTF16LE =

UTF-16-LE Encoding with BOM

INT2NUM(YAML_UTF16LE_ENCODING)
UTF16BE =

UTF-16-BE Encoding with BOM

INT2NUM(YAML_UTF16BE_ENCODING)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(handler = Handler.new) ⇒ Parser

Creates a new Psych::Parser instance with handler. YAML events will be called on handler. See Psych::Parser for more details.



47
48
49
50
 
# File 'lib/psych/parser.rb', line 47

def initialize handler = Handler.new
  @handler = handler
  @external_encoding = ANY
end

Instance Attribute Details

#external_encoding=(value) ⇒ Object (writeonly)

Set the encoding for this parser to encoding



41
42
43
 
# File 'lib/psych/parser.rb', line 41

def external_encoding=(value)
  @external_encoding = value
end

#handler ⇒ Object

The handler on which events will be called



38
39
40
 
# File 'lib/psych/parser.rb', line 38

def handler
  @handler
end

Instance Method Details

#mark ⇒ Object

Returns a Psych::Parser::Mark object that contains line, column, and index information.



508
509
510
511
512
513
514
515
516
517
518
519
520
521
 
# File 'ext/psych/psych_parser.c', line 508

static VALUE mark(VALUE self)
{
    VALUE mark_klass;
    VALUE args[3];
    yaml_parser_t * parser;

    TypedData_Get_Struct(self, yaml_parser_t, &psych_parser_type, parser);
    mark_klass = rb_const_get_at(cPsychParser, rb_intern("Mark"));
    args[0] = SIZET2NUM(parser->mark.index);
    args[1] = SIZET2NUM(parser->mark.line);
    args[2] = SIZET2NUM(parser->mark.column);

    return rb_class_new_instance(3, args, mark_klass);
}

#parse(yaml, path = yaml.respond_to?(:path) ? yaml.path : "<unknown>") ⇒ Object

call-seq:

parser.parse(yaml)

Parse the YAML document contained in yaml. Events will be called on the handler set on the parser instance.

See Psych::Parser and Psych::Parser#handler



61
62
63
 
# File 'lib/psych/parser.rb', line 61

def parse yaml, path = yaml.respond_to?(:path) ? yaml.path : "<unknown>"
  _native_parse @handler, yaml, path
end