What is the most elegant way to encode/decode an Object to Dictionary

Question

The object in question consists of key/value pairs aka @property. Is there an elegant way to encode/decode this object to a dictionary? It seems brute force to manually pull out each attribute and create the dictionary by hand.

Answer 1

Objective-C's "object as dictionary" support comes through Key-Value Coding:

NSArray *myAttributes; // Assume this exists
NSDictionary *dictRepresentation = [object dictionaryWithValuesForKeys:myAttributes];

Answer 2

Does it absolutely need to be a dictionary? Because NSKeyedArchiver gives you the memento-stored-by-key behaviour without actually being an NSDictionary - and has the added bonus that it can archive many objects which property-list serialization doesn't automatically support. There's a good description of using archivers and unarchivers on the CocoaDev wiki.

Answer 3

If the keys you desire are ObjC-2.0 properties of the class in question, you could do something similar to the following:

// Assume MyClass exists
unsigned int count = 0;
objc_property_t *properties = class_copyPropertyList([myClassInstance class], &count);
NSMutableDictionary *propertiesDict = [NSMutableDictionary dictionary];
unsigned int i;
for(i = 0; i < count; ++i) {
  NSString *propertyName = [NSString stringWithCString:property_getName(properties[i]) encoding:NSASCIIStringEncoding];
  id propertyValue = [self valueForKey:propertyName];
  if(propertyValue)
    [propertiesDict setObject:propertyValue forKey:propertyName];
}
free(properties), properties = NULL;
// Do something with propertiesDict

This could also be a simple class extension.