I have a method that needs to return an array of objects. The way it does that now is:
NSMutableArray*alloc-d and init-edaddObjectIs autoreleasing the array the right thing to do? What about the objects inside the array? When should these be released?
Yes, setting the array to autorelease before you return it is a reasonable thing to do. Also, if you are calling alloc and init on the things that you put into the array, you should call release (or autorelease) on each one after you add it to the array. Your objects will still be retained as long as they are in the array. Removing them from the array (or releasing the array) will cause them to be released.
autoreleased NSArray is normally dependant on the name of your method. Following Apple's conventions if you use the words alloc, init or copy in the method name then you should not autorelease as the caller now expects that they own the object and are responsible for releasing it. If your method name does not contain these keywords then autoreleaseing is fine.Your method should set the array to autorelease and then the caller should retain the returned array. So the method is no longer responsible for the array, the caller is.
The objects in the array will be retained by NSMutableArray, so you should set them to autorelease so they don't leak.
- (NSMutableArray*) calleeMethod
{
// this method is retaining the array temporarily
// someone else is responsible for retaining it
NSMutableArray * newArray = [[[NSMutableArray alloc] init] autorelease];
// add some objects
for (int i = 0; i < 10; i++)
{
// autorelease these objects because newArray will retain each item and
// is responsible for the items
FooObject * newFooObject = [[[FooObject alloc] initWithNumber:i] autorelease];
[newArray addObject:newFooObject];
}
return newArray;
}
- (void) callerMethod
{
// retain the returned array, because we own it
mNewArray = [[self calleeMethod] retain];
// do stuff
// make sure you explicitly release mNewArray later (probably in the dealloc)
}
autorelease. The containing array will retain them when added, and release them when they are removed. Just release them yourself after they are added to the array.