NSKeyedUnarchiverunarchiveTopLevelObjectWithDataerror

NSKeyedUnarchiver is a class in Apple's Foundation framework that decodes objects that were encoded with NSKeyedArchiver. It can reconstruct complex object graphs, preserving object identity and relationships, from binary data or files. The decoding process requires that the encoded objects implement the NSCoding protocol, or for modern usage, the NSSecureCoding protocol.

To perform decoding, you supply the archived data to an NSKeyedUnarchiver instance and request objects by key or by top-level object. Historically, developers used unarchiveObjectWithData:, but modern code uses error-based APIs such as unarchiveTopLevelObjectWithData:error:, or decodeObjectOfClass:forKey:/decodeObjectOfClasses:forKey: when secure coding is enabled. These methods can throw or return errors, enabling better error handling.

Security is a key consideration with NSKeyedUnarchiver. Since the introduction of secure coding, developers are encouraged to enable NSSecureCoding in archived data and use the secure decoding APIs to verify the class types being decoded, mitigating object substitution attacks. This often requires that all involved classes conform to NSSecureCoding and declare supportsSecureCoding. See also NSKeyedArchiver and NSSecureCoding.