Module: KeyDial::Coercion::Structs::ClassMethods

Defined in:
lib/key_dial/coercion.rb

Instance Method Summary collapse

Instance Method Details

#from(_obj) ⇒ Object

Allows you to do Struct.from(obj) to instantiate a Struct using keys/values from any object intelligently.



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# File 'lib/key_dial/coercion.rb', line 116

def from(_obj)
  from_obj = _obj
  if !from_obj.is_a?(Struct) && !from_obj.is_a?(Hash) && !from_obj.is_a?(Array)
    return EMPTY if _obj == EMPTY[0]
    return EMPTY if _obj.nil?
    # For non-keyed objects, we will treat the whole object like it's a value to push into the first property of a struct

    from_obj = [_obj]
  end
  
  struct_class = self
  
  # Are we operating on a defined type of Struct?

  if struct_class < Struct
    if from_obj.is_a?(struct_class)
      # Has an instantiation of that type of Struct been passed in? If so, just return it

      return from_obj
    else
      # Get values

      values = []
      if from_obj.is_a?(Array)
        # Get as many elements of array as this Struct can handle - discard the rest

        values = from_obj.first(struct_class.members.size)
      else 
        # Not an Array, so must be another Struct or Hash

        struct_class.members.each { |key|
          if from_obj.key?(key)
            # If the object has this expected key, use it

            values << from_obj[key]
          else
            # Otherwise, fill this key with nil

            values << nil
            # Keys in the from object which don't match expected keys are discarded

          end
        }
      end
      # values now contains a value or nil for each of this class's expected keys

      return struct_class.new(*values)
    end
  else
    # Anonymous Struct

    new_values = from_obj.is_a?(Array) ? from_obj : from_obj.values
    # Iterate over the keys of the from object

    # (Array.keys is monkeypatched in)

    new_keys = from_obj.keys.each_with_index.map { |k, i|
      if k.respond_to?(:to_sym) && k != ''
        k.to_sym
      elsif k.respond_to?(:to_s) && !k.nil?
        k.to_s.to_sym
      else
        # If we can't construct a valid Struct key for this key, we discard the corresponding value

        new_values.delete_at(i)
        nil
      end
    }.reject(&:nil?)
    if new_keys.size > 0
      # Create anonymous Struct with the specified keys and values

      return Struct.new(*new_keys).new(*new_values)
    else
      # Return the Empty Struct

      return EMPTY
    end
  end
  
rescue
  return EMPTY
end