Class: Mechanize::PluggableParser

Inherits:
Object
  • Object
show all
Defined in:
lib/mechanize/pluggable_parsers.rb

Overview

Mechanize allows different parsers for different content types. Mechanize uses PluggableParser to determine which parser to use for any content type. To use your own parser or to change the default parsers, register them with this class through Mechanize#pluggable_parser.

The default parser for unregistered content types is Mechanize::File.

The module Mechanize::Parser provides basic functionality for any content type, so you may use it in custom parsers you write. For small files you wish to perform in-memory operations on, you should subclass Mechanize::File. For large files you should subclass Mechanize::Download as the content is only loaded into memory in small chunks.

When writing your own pluggable parser, be sure to provide a method #body that returns a String containing the response body for compatibility with Mechanize#get_file.

Example

To create your own parser, just create a class that takes four parameters in the constructor. Here is an example of registering a parser that handles CSV files:

require 'csv'

class CSVParser < Mechanize::File
  attr_reader :csv

  def initialize uri = nil, response = nil, body = nil, code = nil
    super uri, response, body, code
    @csv = CSV.parse body
  end
end

agent = Mechanize.new
agent.pluggable_parser.csv = CSVParser
agent.get('http://example.com/test.csv')  # => CSVParser

Now any response with a content type of ‘text/csv’ will initialize a CSVParser and return that object to the caller.

To register a parser for a content type that Mechanize does not know about, use the hash syntax:

agent.pluggable_parser['text/something'] = SomeClass

To set the default parser, use #default:

agent.pluggable_parser.default = Mechanize::Download

Now all unknown content types will be saved to disk and not loaded into memory.

Constant Summary collapse

CONTENT_TYPES = 
{
  :html  => 'text/html',
  :wap   => 'application/vnd.wap.xhtml+xml',
  :xhtml => 'application/xhtml+xml',
  :pdf   => 'application/pdf',
  :csv   => 'text/csv',
  :xml   => ['text/xml', 'application/xml'],
}
InvalidContentTypeError = 
if defined?(MIME::Type::InvalidContentType)
  # For mime-types >=2.1
  MIME::Type::InvalidContentType
else
  # For mime-types <2.1
  MIME::InvalidContentType
end

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ PluggableParser

Returns a new instance of PluggableParser.



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# File 'lib/mechanize/pluggable_parsers.rb', line 84

def initialize
  @parsers = {
    CONTENT_TYPES[:html]  => Mechanize::Page,
    CONTENT_TYPES[:xhtml] => Mechanize::Page,
    CONTENT_TYPES[:wap]   => Mechanize::Page,
    'image'               => Mechanize::Image,
    'text/xml'            => Mechanize::XmlFile,
    'application/xml'     => Mechanize::XmlFile,
  }

  @default = Mechanize::File
end

Instance Attribute Details

#default ⇒ Object

Returns the value of attribute default.



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# File 'lib/mechanize/pluggable_parsers.rb', line 82

def default
  @default
end

Instance Method Details

#[](content_type) ⇒ Object

Retrieves the parser for content_type content



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# File 'lib/mechanize/pluggable_parsers.rb', line 165

def [](content_type)
  @parsers[content_type]
end

#[]=(content_type, klass) ⇒ Object

Sets the parser for content_type content to klass

The content_type may either be a full MIME type a simplified MIME type (‘text/x-csv’ simplifies to ‘text/csv’) or a media type like ‘image’.



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# File 'lib/mechanize/pluggable_parsers.rb', line 175

def []= content_type, klass
  register_parser content_type, klass
end

#csv=(klass) ⇒ Object

Registers klass as the parser for text/csv content



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# File 'lib/mechanize/pluggable_parsers.rb', line 149

def csv=(klass)
  register_parser(CONTENT_TYPES[:csv], klass)
end

#html=(klass) ⇒ Object

Registers klass as the parser for text/html and application/xhtml+xml content



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# File 'lib/mechanize/pluggable_parsers.rb', line 127

def html=(klass)
  register_parser(CONTENT_TYPES[:html], klass)
  register_parser(CONTENT_TYPES[:xhtml], klass)
end

#parser(content_type) ⇒ Object

Returns the parser registered for the given content_type



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# File 'lib/mechanize/pluggable_parsers.rb', line 100

def parser content_type
  return default unless content_type

  parser = @parsers[content_type]

  return parser if parser

  mime_type = MIME::Type.new "content-type" => content_type

  parser = @parsers[mime_type.to_s] ||
           @parsers[mime_type.simplified] ||
           # Starting from mime-types 3.0 x-prefix is deprecated as per IANA
           (@parsers[MIME::Type.simplified(mime_type.to_s, remove_x_prefix: true)] rescue nil) ||
           @parsers[mime_type.media_type] ||
           default
rescue InvalidContentTypeError
  default
end

#pdf=(klass) ⇒ Object

Registers klass as the parser for application/pdf content



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# File 'lib/mechanize/pluggable_parsers.rb', line 142

def pdf=(klass)
  register_parser(CONTENT_TYPES[:pdf], klass)
end

#register_parser(content_type, klass) ⇒ Object

:nodoc:



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# File 'lib/mechanize/pluggable_parsers.rb', line 119

def register_parser content_type, klass # :nodoc:
  @parsers[content_type] = klass
end

#xhtml=(klass) ⇒ Object

Registers klass as the parser for application/xhtml+xml content



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# File 'lib/mechanize/pluggable_parsers.rb', line 135

def xhtml=(klass)
  register_parser(CONTENT_TYPES[:xhtml], klass)
end

#xml=(klass) ⇒ Object

Registers klass as the parser for text/xml content



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# File 'lib/mechanize/pluggable_parsers.rb', line 156

def xml=(klass)
  CONTENT_TYPES[:xml].each do |content_type|
    register_parser content_type, klass
  end
end