findClass {methods} | R Documentation |
Computations with Classes
Description
Functions to find and manipulate class definitions.
Usage
removeClass(Class, where)
isClass(Class, formal=TRUE, where)
getClasses(where, inherits = missing(where))
findClass(Class, where, unique = "")
resetClass(Class, classDef, where)
sealClass(Class, where)
Arguments
Class |
character string name for the class. The functions will
usually take a class definition instead of the string. To restrict
the class to those defined in a particular package, set the
|
where |
The environment in which to modify or remove the definition. Defaults to the top-level environment of the calling function (the global environment for ordinary computations, but the environment or name space of a package in the source for a package). When searching for class definitions, |
unique |
if |
inherits |
in a call to |
formal |
Should a formal definition be required? |
classDef |
For |
Details
These are the functions that test and manipulate formal class definitions. Brief documentation is provided below. See the references for an introduction and for more details.
removeClass
:-
Remove the definition of this class, from the environment
where
if this argument is supplied; if not,removeClass
will search for a definition, starting in the top-level environment of the call toremoveClass
, and remove the (first) definition found. isClass
:-
Is this the name of a formally defined class? (Argument
formal
is for compatibility and is ignored.) getClasses
:-
The names of all the classes formally defined on
where
. If called with no argument, all the classes visible from the calling function (if called from the top-level, all the classes in any of the environments on the search list). Theinherits
argument can be used to search a particular environment and all its parents, but usually the default setting is what you want. findClass
:-
The list of environments or positions on the search list in which a class definition of
Class
is found. Ifwhere
is supplied, this is an environment (or name space) from which the search takes place; otherwise the top-level environment of the caller is used. Ifunique
is supplied as a character string,findClass
returns a single environment or position. By default, it always returns a list. The calling function should select, say, the first element as a position or environment for functions such asget
.If
unique
is supplied as a character string,findClass
will warn if there is more than one definition visible (using the string to identify the purpose of the call), and will generate an error if no definition can be found. resetClass
:-
Reset the internal definition of a class. Causes the complete definition of the class to be re-computed, from the representation and superclasses specified in the original call to
setClass
.This function is called when aspects of the class definition are changed. You would need to call it explicitly if you changed the definition of a class that this class extends (but doing that in the middle of a session is living dangerously, since it may invalidate existing objects).
sealClass
:Seal the current definition of the specified class, to prevent further changes. It is possible to seal a class in the call to
setClass
, but sometimes further changes have to be made (e.g., by calls tosetIs
). If so, callsealClass
after all the relevant changes have been made.
References
Chambers, John M. (2008) Software for Data Analysis: Programming with R Springer. (For the R version.)
Chambers, John M. (1998) Programming with Data Springer (For the original S4 version.)
See Also
setClassUnion
,
Methods
,
makeClassRepresentation