NSCoder and custom types

Question

How do you use NSCoder to encode and decode custom types?

For example, how would you use NSCoder with an instance of "STATE" where:

typedef enum { ON, OFF } STATE;

Citrate

Answer 1

You can treat them as integers as they are implicitly assigned integer values:

- (void) encodeWithCoder: (NSCoder *)coder {
  ...
  [coder encodeInt:type forKey:@"state"];
}

- (id) initWithCoder: (NSCoder *)coder {
  ...
  state = [coder decodeIntForKey:@"state"];
}

Ronni

Except that a change in the order internally in the enum would break the coding. – Midkiff

And what class do you put these methods? They are types, not objects... NSKeyedArchiver? – Foreclose

To support encoding and decoding of instances, a class must adopt the NSCoding protocol and implement its methods. An object being encoded or decoded is responsible for encoding and decoding its state. – Ronni

You can encode an additional "objectVersion" identifier to account for differences that may occur in enum order as the object architecture evolves. An enum is also signed, so you can squeeze in negative values which may help in some circumstances. – Primate