Class: MicroformatParser::Extractor

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

Overview

Implements an extractor using a simple expression format.

For more information see MicroformatParser.extractor.

Constant Summary collapse

REGEX =

Parse each extractor into three parts: $1 function name (excluding parentheses) $2 element name $3 attribute name (including leading @) If a match is found the result is either $1, or $2 and/or $3

/^(\w+)\(\)|([A-Za-z][A-Za-z0-9_\-:]*)?(@[A-Za-z][A-Za-z0-9_\-:]*)?$/

Instance Method Summary collapse

Constructor Details

#initialize(context, statement) ⇒ Extractor

:startdoc:

Raises:



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# File 'lib/uformatparser.rb', line 612

def initialize(context, statement)
    statement.strip!
    @extracts = []
    # Break the statement into multiple extraction rules, separated by |.
    statement.split('|').each do |extract|
        parts = REGEX.match(extract)
        if parts[1] then
            # Function. Find a method in the context object (the rule class),
            # report an error is not found.
            begin
                @extracts << context.method(parts[1]) # context.
            rescue NameError=>error
                raise InvalidExtractorException, error.message, error.backtrace
            end
        elsif parts[2] and parts[3]
            # Apply only if element of this type, and extract the named attribute.
            attr_name = parts[3][1..-1]
            @extracts << proc { |node| node.attributes[attr_name] if node.name == parts[2] }
        elsif parts[2]
            # Apply only if element of this type, and extract the text value.
            @extracts << proc { |node| text(node) if node.name == parts[2] }
        elsif parts[3]
            # Extract the named attribute.
            attr_name = parts[3][1..-1]
            @extracts << proc { |node| node.attributes[attr_name] }
        else
            raise InvalidExtractorException, "Invalid extraction statement"
        end
    end
    raise InvalidExtractorException, "Invalid (empty) extraction statement" if @extracts.size == 0
end

Instance Method Details

#extract(node) ⇒ Object

Extracts a value from the node based on the extractor expression.



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# File 'lib/uformatparser.rb', line 646

def extract(node)
    # Iterate over all extraction rules, returning the first value.
    value = nil
    @extracts.each do |extract|
        value = extract.call(node)
        break if value
    end
    value
end

#inspect ⇒ Object 



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# File 'lib/uformatparser.rb', line 656

def inspect
    @extracts.join('|')
end