Question

In one of my classes I have a derived property called items, it is basically like:

- (NSArray *)items
{
    [self.unsortedSet.allValues sortedArrayUsingDescriptor:...];
}

then in some other place:

[self.items enumerateUsingBlock...{
    // do something with item
}]

in this case, if self.items has X items, then does the enumeration block generate self.items X times? Or is it more safer to:

NSArray *sortedItems = self.items;
[sortedItems enumerateUsingBlock...{}]

Answer 1

then does the enumeration block generate self.items X times?

No. Just once. This is for semantics and efficiency.

Or is it more safe to…

semantics depend on your implementation.