Class

NSKeyedUnarchiver

A decoder that restores data from an archive referenced by keys.

Overview

NSKeyedUnarchiver, 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 NSKeyedArchiver class.

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, decodeBoolForKey: returns NO, decodeIntForKey: returns 0, and decodeObjectForKey: returns nil.

NSKeyedUnarchiver 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 NSRangeException. Further, when trying to coerce a value to an incompatible type, for example decoding an int as a float, the decoding method throws an NSInvalidUnarchiveOperationException.

Topics

Initializing a Keyed Unarchiver

initForReadingWithData:

Initializes the receiver for decoding an archive previously encoded by NSKeyedArchiver.

Unarchiving Data

unarchiveObjectWithData:

Decodes and returns the object graph previously encoded by NSKeyedArchiver and stored in a given NSData object.

unarchiveObjectWithFile:

Decodes and returns the object graph previously encoded by NSKeyedArchiver written to the file at a given path.

requiresSecureCoding

Indicates whether the receiver requires all unarchived classes to conform to NSSecureCoding.

Decoding Data

containsValueForKey:

Returns a Boolean value that indicates whether the archive contains a value for a given key within the current decoding scope.

decodeBoolForKey:

Decodes a Boolean value associated with a given key.

decodeBytesForKey:returnedLength:

Decodes a stream of bytes associated with a given key.

decodeDoubleForKey:

Decodes a double-precision floating-point value associated with a given key.

decodeFloatForKey:

Decodes a single-precision floating-point value associated with a given key.

decodeIntForKey:

Decodes an integer value associated with a given key.

decodeInt32ForKey:

Decodes a 32-bit integer value associated with a given key.

decodeInt64ForKey:

Decodes a 64-bit integer value associated with a given key.

decodeObjectForKey:

Decodes and returns an object associated with a given key.

finishDecoding

Tells the receiver that you are finished decoding objects.

Managing the Delegate

delegate

The receiver’s delegate.

Managing Class Names

setClass:forClassName:

Adds a class translation mapping to NSKeyedUnarchiver whereby objects encoded with a given class name are decoded as instances of a given class instead.

classForClassName:

Returns the class from which NSKeyedUnarchiver instantiates an encoded object with a given class name.

setClass:forClassName:

Adds a class translation mapping to the receiver whereby objects encoded with a given class name are decoded as instances of a given class instead.

classForClassName:

Returns the class from which the receiver instantiates an encoded object with a given class name.

Constants

Keyed Unarchiving Exception Names

Names of exceptions that are raised by NSKeyedUnarchiver if there is a problem extracting an archive.

Instance Properties

Relationships

Inherits From

See Also

Keyed Archivers

NSKeyedArchiver

A coder that stores an object's data to an archive referenced by keys.

NSKeyedArchiverDelegate

The optional methods implemented by the delegate of a keyed archiver.

NSKeyedUnarchiverDelegate

The optional methods implemented by the delegate of a keyed unarchiver.

NSCoder

An abstract class that serves as the basis for objects that enable archiving and distribution of other objects.