Standard type mappings

Basic types

ActionScript	Objective-C	Notes
null, undefined	NSNull
String	NSString
Boolean	NSNumber	NSNumber containing a Bool value converts to a Boolean
Number	NSNumber	NSNumber containing a numeric value converts to a Number
Date	NSDate
XML	NSString
Array	NSArray
Object	NSDictionary
RecordSet	not supported

AMF3

ActionScript	Objective-C
int, uint	NSNumber
ByteArray	NSData

Flex

ActionScript	Objective-C
ObjectProxy	FlexObjectProxy
ArrayCollection	FlexArrayCollection
AbstractMessage	FlexAbstractMessage
AcknowledgeMessage	FlexAcknowledgeMessage
CommandMessage	FlexCommandMessage
ErrorMessage	FlexErrorMessage
RemotingMessage	FlexRemotingMessage
DataMessage	not supported
SequencedMessage	not supported
PagedMessage	not supported
DataErrorMessage	not supported

Niceties

There are three options to improve handling of ArrayCollections and ObjectProxies.
By setting

[AMFUnarchiver setOptions:(AMFUnarchiverUnpackArrayCollection | AMFUnarchiverUnpackObjectProxyOption)];

ArrayCollections will automatically be deserialized to ordinary NSArrays and ObjectProxies to NSDictionaries.

You can also set

[AMFArchiver setOptions:AMFArchiverPackArrayOption];

in order to serialize NSArrays into ArrayCollections.