当NSKeyedUnarchiver遇到未知类时，unarchiver(_:cannotDecodeObjectOfClassName:originalClasses:)将调用委托方法。
委托可以例如加载一些代码以将类引入运行时并返回该类，或者 。如果委托返回nil，则取消归档将中止，并且该方法将引发一个NSInvalidUnarchiveOperationException。
因此，您可以像这样实现委托：
class MyUnArchiverDelegate: NSObject, NSKeyedUnarchiverDelegate {
// This class is placeholder for unkNown classes.
// It will eventually be `nil` when decoded.
final class UnkNown: NSObject, NSCoding {
init?(coder aDecoder: NSCoder) { super.init(); return nil }
func encodeWithCoder(aCoder: NSCoder) {}
}
func unarchiver(unarchiver: NSKeyedUnarchiver, cannotDecodeObjectOfClassName name: String, originalClasses classNames: [String]) -> AnyClass? {
return UnkNown.self
}
}
然后：
let unarchiver = NSKeyedUnarchiver(forReadingWithData: dat)
let delegate = MyUnArchiverDelegate()
unarchiver.delegate = delegate
unarchiver.decodeObjectForKey("root")
// -> `nil` if the root object is unkNown class.
：
我没有注意到它NSCoder具有extension更快的方法：
extension NSCoder {
@warn_unused_result
public func decodeObjectOfClass<DecodedObjectType : NSCoding where DecodedObjectType : NSObject>(cls: DecodedObjectType.Type, forKey key: String) -> DecodedObjectType?
@warn_unused_result
@nonobjc public func decodeObjectOfClasses(classes: NSSet?, forKey key: String) -> AnyObject?
@warn_unused_result
public func decodeTopLevelObject() throws -> AnyObject?
@warn_unused_result
public func decodeTopLevelObjectForKey(key: String) throws -> AnyObject?
@warn_unused_result
public func decodeTopLevelObjectOfClass<DecodedObjectType : NSCoding where DecodedObjectType : NSObject>(cls: DecodedObjectType.Type, forKey key: String) throws -> DecodedObjectType?
@warn_unused_result
public func decodeTopLevelObjectOfClasses(classes: NSSet?, forKey key: String) throws -> AnyObject?
}
您可以：
do {
try unarchiver.decodeTopLevelObjectForKey("root")
// OR `unarchiver.decodeTopLevelObject()` depends on how you archived.
}
catch let (err) {
print(err)
}
// -> emits something like:
// Error Domain=NSCocoaErrorDomain Code=4864 "*** -[NSKeyedUnarchiver decodeObjectForKey:]: cannot decode object of class (MyProject.MyClass) for key (root); the class may be defined in source code or a library that is not linked" UserInfo={NSDebugDescription=*** -[NSKeyedUnarchiver decodeObjectForKey:]: cannot decode object of class (MyProject.MyClass) for key (root); the class may be defined in source code or a library that is not linked}
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