protocol CodingKey A type that can be used as a key for encoding and decoding. Inheritance CustomDebugStringConvertible, CustomStringConvertible Initializers init init?(intValue:) Required Creates a new instance from the specified integer. If the value passed as intValue does not correspond to any instance of this type, the result is nil. parameter intValue: The integer value of the desired key. Declaration init?(intValue: Int) init init?(stringValue:) Required Creates a new instance from the given string. If the string passed as stringValue does not correspond to any instance of this type, the result is nil. parameter stringValue: The string value of the desired key. Declaration init?(stringValue: String) Instance Variables var intValue Required The value to use in an integer-indexed collection (e.g. an int-keyed dictionary). Declaration var intValue: Int? var stringValue Required The string to use in a named collection (e.g. a string-keyed dictionary). Declaration var stringValue: String