A decoder that restores data from an archive referenced by keys.
- iOS 2.0+
- macOS 10.2+
- tvOS 9.0+
- watchOS 2.0+
NSKeyed, a concrete subclass of
NSCoder, defines methods for decoding a set of named objects (and scalar values) from a keyed archive. Such archives are produced by instances of the
A keyed archive is encoded as a hierarchy of objects. Each object in the hierarchy serves as a namespace into which other objects are encoded. The objects available for decoding are restricted to those that were encoded within the immediate scope of a particular object. Objects encoded elsewhere in the hierarchy, whether higher than, lower than, or parallel to this particular object, are not accessible. In this way, the keys used by a particular object to encode its instance variables need to be unique only within the scope of that object.
If you invoke one of the
decode... methods of this class using a key that does not exist in the archive, a non-positive value is returned. This value varies by decoded type. For example, if a key does not exist in an archive,
NSKeyed supports limited type coercion. A value encoded as any type of integer, whether a standard int or an explicit 32-bit or 64-bit integer, can be decoded using any of the integer decode methods. Likewise, a value encoded as a float or double can be decoded as either a float or a double value. If an encoded value is too large to fit within the coerced type, the decoding method throws a
NSRange. Further, when trying to coerce a value to an incompatible type, for example decoding an int as a float, the decoding method throws an