To implement NSCopying, your object must respond to the -copyWithZone:
selector. Here’s how you declare that you conform to it:
@interface MyObject : NSObject <NSCopying> {
Then, in your object’s implementation (your .m
file):
- (id)copyWithZone:(NSZone *)zone
{
// Copying code here.
}
What should your code do? First, create a new instance of the object—you can call [[[self class] alloc] init]
to get an initialized obejct of the current class, which works well for subclassing. Then, for any instance variables that are a subclass of NSObject
that supports copying, you can call [thatObject copyWithZone:zone]
for the new object. For primitive types (int
, char
, BOOL
and friends) just set the variables to be equal. So, for your object Vendor, it’d look like this:
- (id)copyWithZone:(NSZone *)zone
{
id copy = [[[self class] alloc] init];
if (copy) {
// Copy NSObject subclasses
[copy setVendorID:[[self.vendorID copyWithZone:zone] autorelease]];
[copy setAvailableCars:[[self.availableCars copyWithZone:zone] autorelease]];
// Set primitives
[copy setAtAirport:self.atAirport];
}
return copy;
}