deep copy

For a class to make deep copies, the three methods below must be provided.

Instead of doing a deep copy right away, there are some optimization strategies that can be used.

But where the value is a mutable object it must be deep copied.

"The recording machines made a deep copy of her.

When deep copies of objects have to be made, exception safety should be taken into consideration.

Hence, the operation not only forgoes the expense of a deep copy, but is safe and invisible.

An alternative is a deep copy.

If we write our own copy constructor that performs a deep copy then this problem goes away.

The Eiffel class contains features for shallow and deep copying and cloning of objects.

A chronic performance problem with C++03 is the costly and unnecessary deep copies that can happen implicitly when objects are passed by value.

With complex object graphs deep copying can become problematic, with recursive references.

Lazy copy looks to the outside just as a deep copy but takes advantage of the speed of a shallow copy whenever possible.

Deep copying and creating deep twins can be done using the features and , again inherited from class .

For deep copies an explicit copy constructor that makes deep copies is required.

In Python, the library's copy module provides shallow copy and deep copy of objects through the and functions, respectively.

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 necessary.

Deep copies may be achieved by dumping and loading an object's byte stream or YAML serialization.

Some utilities attempt to overcome these issues by using reflection to deep copy objects, such as generic deep copy and the deep-cloning library.

When a class desires a deep copy or some other custom behavior, they must perform that in their own method after they obtain the copy from the superclass.

Deep copy and persistence of a BWidget's Tree (BWidget Trees)

In computer science, the term value type is commonly used to refer to one of two kinds of data types: Types of values or Types of objects with deep copy semantics.

Other programming languages-e.g., Java-do not formally define the term value type, but their practitioners informally use the term to refer to types with deep copy semantics (such as Java's primitive types).

The proxy generates future objects for representing future values, transforms calls into Request objects (in terms of metaobject, this is a reification) and performs deep copies of passive objects passed as parameters.

This is typically used for persistence and wire protocol purposes, but it does create copies of objects and, unlike clone, a deep copy that gracefully handles cycled graphs of objects is readily available with minimal effort from the programmer.

After obtaining a copy from the parent class, a class' own clone() method may then provide custom cloning capability, like deep copying (i.e. duplicate some of the structures referred to by the object) or giving the new instance a new unique ID.