encodeInt64forKey

encodeInt64forKey is a method used in the NSCoder family to encode a 64-bit signed integer with a specific key during the archiving process. It forms part of keyed archiving, where data is written to an archive with string keys and later read back with the same keys. The method is used alongside its counterpart decodeInt64ForKey:, which retrieves the previously encoded value from the archive. The value encoded must be a 64-bit integer (Int64 in Swift, long long in C/Obj-C environments).

In Objective-C, the typical usage is [coder encodeInt64:theValue forKey:@"theKey"]; When decoding, you would use [decoder decodeInt64ForKey:@"theKey"];. In Swift, the equivalent calls are coder.encodeInt64(theValue, forKey: "theKey") and let value = decoder.decodeInt64(forKey: "theKey"). These calls rely on matching keys to preserve data integrity between encoding and decoding sessions.

Common use cases include persisting model objects to disk, caching numeric identifiers, or sharing data across processes or components that use a consistent archiving format. Because the approach relies on explicit keys, it is important to keep a stable key naming convention and to ensure the type remains Int64 across saves and loads.

Notes: encodeInt64forKey is typically used with NSKeyedArchiver/NSKeyedUnarchiver or other NSCoder-based archives. It is one of several scalar encoders offered by NSCoder, alongside encodeInt32, encodeDouble, and similar methods. See also NSCoder, NSKeyedArchiver, NSKeyedUnarchiver, and decodeInt64ForKey for related functionality.