class Psych::Parser

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.

Constants

ANY: Let the parser choose the encoding
UTF16BE: UTF-16-BE Encoding with BOM
UTF16LE: UTF-16-LE Encoding with BOM
UTF8: UTF-8 Encoding

Attributes

external_encoding [W]

Set the encoding for this parser to encoding

handler [RW]

The handler on which events will be called

Public Class Methods

new (handler = Handler.new)

Source

# File vendor/bundle/ruby/3.4.0/gems/psych-5.2.3/lib/psych/parser.rb, line 47
def initialize handler = Handler.new
  @handler = handler
  @external_encoding = ANY
end

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

Public Instance Methods

mark # → #<Psych::Parser::Mark>

Source

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);
}

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

parse(yaml)

Source

# File vendor/bundle/ruby/3.4.0/gems/psych-5.2.3/lib/psych/parser.rb, line 61
def parse yaml, path = yaml.respond_to?(:path) ? yaml.path : "<unknown>"
  _native_parse @handler, yaml, path
end

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