---
name: "oo_copy"
section: "3tcl"
platform: "linux"
package: "tcl8.6-doc"
version: "8.6.16+dfsg-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/oo_copy"
---

# oo\_copy(3tcl)

create copies of objects and classes

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## NAME

oo::copy - create copies of objects and classes

## SYNOPSIS

```
package require TclOO
oo::copy sourceObject ?targetObject? ?targetNamespace?
```

```

```

## DESCRIPTION

The **oo::copy** command creates a copy of an object or class. It takes the name of the object or class to be copied, *sourceObject*, and optionally the name of the object or class to create, *targetObject*, which will be resolved relative to the current namespace if not an absolute qualified name and *targetNamespace* which is the name of the namespace that will hold the internal state of the object (**my** command, etc.); it *must not* refer to an existing namespace. If either *targetObject* or *targetNamespace* is omitted or is given as the empty string, a new name is chosen. Names, unless specified, are chosen with the same algorithm used by the **new** method of **oo::class**. The copied object will be of the same class as the source object, and will have all its per-object methods copied. If it is a class, it will also have all the class methods in the class copied, but it will not have any of its instances copied.

After the *targetObject* has been created and all definitions of its configuration (e.g., methods, filters, mixins) copied, the **\<cloned\>** method of *targetObject* will be invoked, to allow for customization of the created object such as installing related variable traces. The only argument given will be *sourceObject*. The default implementation of this method (in **oo::object**) just copies the procedures and variables in the namespace of *sourceObject* to the namespace of *targetObject*. If this method call does not return a result that is successful (i.e., an error or other kind of exception) then the *targetObject* will be deleted and an error returned.

The result of the **oo::copy** command will be the fully-qualified name of the new object or class.

## EXAMPLES

This example creates an object, copies it, modifies the source object, and then demonstrates that the copied object is indeed a copy.

```
oo::object create src
oo::objdefine src method msg {} {puts foo}
oo::copy src dst
oo::objdefine src method msg {} {puts bar}
src msg              → prints "bar"
dst msg              → prints "foo"
```

## SEE ALSO

oo::class(3tcl), oo::define(3tcl), oo::object(3tcl)

## KEYWORDS

clone, copy, duplication, object