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