Method: Janeway::Functions#parse_function_value

Defined in:
lib/janeway/functions/value.rb

#parse_function_value ⇒ Object

Parameters:

1. NodesType

Result:

ValueType

The value() function extension provides a way to convert an instance of NodesType to a value and make that available for further processing in the filter expression:

Its only argument is an instance of NodesType (possibly taken from a filter-query, as in the example above). The result is an instance of ValueType.

If the argument contains a single node, the result is the value of the node.

If the argument is the empty nodelist or contains multiple nodes, the result is Nothing.

Note: A singular query may be used anywhere where a ValueType is expected, so there is no need to use the value() function extension with a singular query.

Examples:

$[?value(@..color) == “red”]

Raises:



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# File 'lib/janeway/functions/value.rb', line 29

def parse_function_value
  consume # function
  raise "expect group_start token, found #{current}" unless current.type == :group_start

  consume # (

  # Read parameter
  parameters = [parse_function_parameter]
  raise Error, 'Too many parameters for value() function call' unless current.type == :group_end

  AST::Function.new('value', parameters) do |nodes|
    if nodes.is_a?(Array) && nodes.size == 1
      nodes.first
    else
      :nothing
    end
  end
end