R: Loading and Unloading Namespaces

ns-load {base}

R Documentation

Loading and Unloading Namespaces

Description

Functions to load and unload namespaces.

Usage

attachNamespace(ns, pos = 2, dataPath = NULL, depends = NULL)
loadNamespace(package, lib.loc = NULL,
              keep.source = getOption("keep.source.pkgs"),
              partial = FALSE)
requireNamespace(package, ..., quietly = FALSE)
loadedNamespaces()
unloadNamespace(ns)

Arguments

`ns`	string or namespace object.
`pos`	integer specifying position to attach.
`dataPath`	path to directory containing a database of datasets to be lazy-loaded into the attached environment.
`depends`	`NULL` or a character vector of dependencies to be recorded in object `.Depends` in the package.
`package`	string naming the package/namespace to load.
`lib.loc`	character vector specifying library search path.
`keep.source`	Now ignored except during package installation. For more details see this argument to `library`.
`partial`	logical; if true, stop just after loading code.
`quietly`	logical: should progress and error messages be suppressed?
`...`	further arguments to be passed to `loadNamespace`.

Details

The functions loadNamespace and attachNamespace are usually called implicitly when library is used to load a name space and any imports needed. However it may be useful to call these functions directly at times.

loadNamespace loads the specified namespace and registers it in an internal data base. A request to load a namespace when one of that name is already loaded has no effect. The arguments have the same meaning as the corresponding arguments to library, whose help page explains the details of how a particular installed package comes to be chosen. After loading, loadNamespace looks for a hook function named .onLoad as an internal variable in the namespace (it should not be exported). This function is called with the same arguments as .First.lib. Partial loading is used to support installation with the --lazy option.

loadNamespace does not attach the namespace it loads to the search path. attachNamespace can be used to attach a frame containing the exported values of a namespace to the search path (but this is almost always done via library). The hook function .onAttach is run after the namespace exports are attached.

requireNamespace is a wrapper for loadNamespace analogous to require that returns a logical value.

loadedNamespaces returns a character vector of the names of the loaded namespaces.

unloadNamespace can be used to attempt to force a namespace to be unloaded. If the namespace is attached, it is first detached, thereby running a .Last.lib function in the namespace if one is exported. Then an error is signaled if the namespace is imported by other loaded namespaces, and the namespace is not unloaded. If defined, a hook function .onUnload is run before removing the namespace from the internal registry.

See the comments in the help for detach about some issues with unloading and reloading namespaces.

Value

attachNamespace returns invisibly the package environment it adds to the search path.

loadNamespace returns the namespace environment, either one already loaded or the one the function causes to be loaded.

requireNamespace returns TRUE if it succeeds or FALSE.

loadedNamespaces returns a character vector.

unloadNamespace returns NULL, invisibly.

Author(s)

Luke Tierney and R-core

[Package base version 2.15.1 Index]