---
name: "is"
section: "n"
platform: "linux"
package: "tcl"
version: "8.6.16-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/is/n"
---

# is(n)

test argument to see if it is a class or an object

```

```

## NAME

itcl::is - test argument to see if it is a class or an object

## SYNOPSIS

**itcl::is** *option* ?*arg arg ...*?

```

```

## DESCRIPTION

The **is** command is used to check if the argument given is a class or an object; depending on the option given. If the argument if a class or object, then 1 is returned. Otherwise, 0 is returned. The **is** command also recognizes the commands wrapped in the itcl **code** command.

The *option* argument determines what action is carried out by the command.  The legal *options* (which may be abbreviated) are:

- **is class** *command*

  Returns 1 if command is a class, and returns 0 otherwise.

  The fully qualified name of the class needs to be given as the *command* argument. So, if a class resides in a namespace, then the namespace needs to be specified as well. So, if a class **C** resides in a namespace **N**, then the command should be called like:

  ```
  is N::C
      or
  is ::N::C
  ```

- **is** object ?**-class** *className*? *command*

  Returns 1 if *command* is an object, and returns 0 otherwise.

  If the optional "**-class**" parameter is specified, then the *command* will be checked within the context of the class given. Note that *className* has to exist. If not, then an error will be given. So, if *className* is uncertain to be a class, then the programmer will need to check it's existance beforehand, or wrap it in a catch statement.

  So, if **c** is an object in the class **C**, in namespace N then these are the possibilities (all return 1):

  ```
  set obj [N::C c]
  itcl::is object N::c
  itcl::is object c
  itcl::is object $obj
  itcl::is object [itcl::code c]
  ```

## KEYWORDS

class, object