Managing State

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Archiving Custom Objects in Other Applications

Custom classes that can't take advantage of an EOEditingContext for archiving must take a different approach. These classes still must conform to the NSCoding protocol and implement its encodeWithCoder: and initWithCoder: methods; however, you must implement them differently. In encodeWithCoder:, you use the coder argument provided to encode the object's instance variables. In initWithCoder:, the object uses the decoder provided to initialize itself.

For example:

- encodeWithCoder:(NSCoder *)coder {

	[coder encodeObject:carID];

	[coder encodeObject:colorID];

	[coder encodeObject:colorPicture];

	[coder encodeObject:packagesIDs];

	[coder encodeObject:downPayment];

	[coder encodeObject:leaseTerm];

}



- initWithCoder:(NSCoder *)coder {

	self = [super init];

	carID = [[coder decodeObject] retain];

	colorID = [[coder decodeObject] retain];

	colorPicture = [[coder decodeObject] retain];

	packagesIDs = [[coder decodeObject] retain];

	downPayment = [[coder decodeObject] retain];

	leaseTerm = [[coder decodeObject] retain];

	car = nil;

	return self;

}

The Java version of the same example looks like this:

public void encodeWithCoder(NSCoder coder) {

	coder.encodeObject(leaseTerm);

	coder.encodeObject(downPayment);

// The custom Car object that contains all other info about the car.

	coder.encodeObject(car);

}



public ShoppingCart(NSCoder coder) {

	super();

	leaseTerm = coder.decodeObject();

	downPayment = coder.decodeObject();

	Car aCar = (Car)coder.decodeObject();

	setCar(aCar);

}

For more information on archiving, see the class specifications for NSCoding, NSCoder, NSArchiver, and NSUnarchiver in the Foundation Framework Reference.

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