Class: MicroformatParser::Rule

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

Overview

Implements a rule.

A rule identifies matching nodes using a selector, and a means to extract their value using an extractor. The rule also identifies an instance variable and attribute accessor to retrieve the extracted value, and the cardinality of that value.

For more information see MicroformatParser.rule.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, selector, extractor, limit) ⇒ Rule

Returns a new instance of Rule.



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# File 'lib/uformatparser.rb', line 380

def initialize(name, selector, extractor, limit)
    # Change the rule name to the attribute name holding the result
    @name = "@#{name.to_s}".to_sym
    @selector = selector
    @extractor = extractor
    @limit = limit
end

Instance Attribute Details

#extractor ⇒ Object (readonly)

The rule extractor



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# File 'lib/uformatparser.rb', line 378

def extractor
  @extractor
end

#limit ⇒ Object

The rule cardinality (or value limit)

0

No value (disabled)

1

First value extracted

n

Up to n values (array)

-1

Unbound (array)



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# File 'lib/uformatparser.rb', line 374

def limit
  @limit
end

#name ⇒ Object (readonly)

The instance variable/attribute accessor name.



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# File 'lib/uformatparser.rb', line 368

def name
  @name
end

#selector ⇒ Object (readonly)

The rule selector



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# File 'lib/uformatparser.rb', line 376

def selector
  @selector
end

Instance Method Details

#inspect ⇒ Object 



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# File 'lib/uformatparser.rb', line 432

def inspect
    @selector ? "[to #{@name} from #{@selector.inspect}, #{@extractor.inspect}, limit #{@limit}]" : "[to #{@name} from #{@extractor.inspect}, limit #{@limit}]"
end

#process(node, context) ⇒ Object

Called to process this rule on a node with a context object.

Returns true if the rule was processed and should be reduced (not applied to any child nodes). Otherwise, returns false.



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# File 'lib/uformatparser.rb', line 392

def process(node, context)
    # Do nothing if rule is disabled (limit = 0), reduce it.
    return true if @limit == 0
    # Do nothing if rule is singular (limit = 1) and a value was already set
    current = context.instance_variable_get(@name)
    return true if @limit == 1 and current
    # Match the current node, do nothing if not matched
    # (Selector may be nil if rule created to wrap a proc)
    if @selector
        return false unless @selector.instance_of?(UnboundMethod) ? @selector.bind(context).call(node) :
            @selector.instance_of?(Selector) ? @selector.match(node) : @selector.call(node)
    end
    # Extract the value. Do nothing if nothing extracted
    value = case @extractor
    when UnboundMethod
        @extractor.bind(context).call(node)
    when Extractor
        @extractor.extract(node)
    when Proc, Method
        @extractor.call(node)
    when Class
        @extractor.parse(node)
    end
    return false unless value
    # If limit=1, set the new value (singular)
    # If no current value, create new array with new value
    # Otherwise, if no limit or limit not reach, append value to
    # existing array
    if @limit == 1
        context.instance_variable_set(@name, value)
    elsif not current
        context.instance_variable_set(@name, [value])
    elsif current.instance_of? Array and (@limit < 0 or current.size < @limit)
        current << value
    end
    # We always return true, since there's no point in applying
    # the rule to any child nodes.
    return true
end