Class: Yasf::Scraper

Inherits:
Object
  • Object
show all
Includes:
HTTParty
Defined in:
lib/yasf/scraper.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(source, options = nil) ⇒ Scraper

The argument source is a String (url format), or Nokogiri::XML::Element



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# File 'lib/yasf/scraper.rb', line 117

def initialize(source, options = nil)
  @options = options || {}
  case source
  when String
    @document = Nokogiri::HTML(self.class.get(source,@options).body)
  when Nokogiri::XML::Element
    @document = source
  else
    raise ArgumentError, "source not recognized"
  end
end

Class Method Details

.extract_from(source, options = nil) ⇒ Object 



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# File 'lib/yasf/scraper.rb', line 10

def extract_from(source, options = nil)
  self.new(source, options).extract
end

.extractor(map) ⇒ Object

Creates an extractor that will extract values from the selected element and place them in instance variables of the scraper.



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# File 'lib/yasf/scraper.rb', line 50

def extractor(map)
  extracts = []
  map.each_pair do |target, source|
    source = extract_value_from(source)
    target = extract_value_to(target)
    define_method :__extractor do |element|
      value = source.call(element)
      target.call(self, value) unless value.nil?
    end
    extracts << instance_method(:__extractor)
    remove_method :__extractor
  end
  lambda do |element|
    extracts.each do |extract|
      extract.bind(self).call(element)
    end
    true
  end
end

.result(*symbols) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/yasf/scraper.rb', line 33

def result(*symbols)
  raise ArgumentError, "one symbol to return the value of this accessor" if symbols.empty?
  symbols = symbols.map {|s| s.to_sym}
  if symbols.size == 1
    define_method :result do
      return self.send(symbols[0])
    end
  else
    struct = Struct.new(*symbols)
    define_method :result do
      return struct.new(*symbols.collect {|s| self.send(s) })
    end
  end
end

.rules ⇒ Object

Returns an array of scraper rules



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# File 'lib/yasf/scraper.rb', line 29

def rules()
  @rules ||= []
end

.scrape(*args) ⇒ Object

Defines a processing rule.

Raises:

  • (ArgumentError) 


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# File 'lib/yasf/scraper.rb', line 15

def scrape(*args)
  name = args.shift if args.first.is_a?(Symbol)
  if args.last.is_a?(Hash)
    extractor = extractor(args.pop)
  end
  raise ArgumentError, "Missing extractor: the last argument tells us what to extract" unless extractor
  raise ArgumentError, "Missing selector: the first argument tells us what to select" if args.empty?
  define_method :__extractor, extractor
  method = instance_method(:__extractor)
  remove_method :__extractor
  rules << [args.pop, method, name]
end

Instance Method Details

#collect ⇒ Object

Called by #scrape before calling #result typically used to run post-processing steps



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# File 'lib/yasf/scraper.rb', line 135

def collect()
end

#document ⇒ Object

Returns the document being processed.



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# File 'lib/yasf/scraper.rb', line 130

def document
  @document
end

#extract ⇒ Object

Scrapes the document and returns the result.



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# File 'lib/yasf/scraper.rb', line 139

def extract
  rules = self.class.rules.clone
  rules.delete_if do |selector, extractor, rule_name|
    document.search(selector).each do |element|
      extractor.bind(self).call(element)
    end
  end
  collect
  return result
end