Editing Object copying (section)

=== Lazy copy ===

A lazy copy is an implementation of a deep copy. When initially copying an object, a (fast) shallow copy is used. A counter is also used to track how many objects share the data. When the program wants to modify an object, it can determine if the data is shared (by examining the counter) and can do a deep copy if needed.

Lazy copy looks to the outside just as a deep copy, but takes advantage of the speed of a shallow copy whenever possible. The downside are rather high but constant base costs because of the counter. Also, in certain situations, [[circular reference]]s can cause problems.

Lazy copy is related to [[copy-on-write]].