R: Method Utilities

RMethodUtils {methods} | R Documentation

## Method Utilities

### Description

Utility functions to support the definition and use of formal methods. Most of these functions will not normally be called directly by the user.

### Usage

    getGeneric(f, mustFind=FALSE, where, package)

    getGroup(fdef, recursive, where)
    getGroupMembers(group, recursive = FALSE, character = TRUE)

    getMethodsMetaData(f, where)
    assignMethodsMetaData (f, value, fdef, where, deflt)

    makeGeneric(f, fdef, fdefault =, group=list(), valueClass=character(),
                package =, signature = NULL, genericFunction = NULL,
                simpleInheritanceOnly = NULL)

    makeStandardGeneric(f, fdef)

    generic.skeleton(name, fdef, fdefault)

    defaultDumpName(generic, signature)

    doPrimitiveMethod(name, def, call= sys.call(sys.parent()),
                      ev = sys.frame(sys.parent(2)))

    conformMethod(signature, mnames, fnames, f= , fdef, method)

    matchSignature(signature, fun, where)

    findUnique(what, message, where)

    MethodAddCoerce(method, argName, thisClass, methodClass)

    cacheMetaData(where, attach = TRUE, searchWhere = as.environment(where),
                  doCheck = TRUE)

    cacheGenericsMetaData(f, fdef, attach = TRUE, where, package, methods)

    setPrimitiveMethods(f, fdef, code, generic, mlist)

    missingArg(symbol, envir = parent.frame(), eval)

    balanceMethodsList(mlist, args, check = TRUE)

    sigToEnv(signature, generic)

    rematchDefinition(definition, generic, mnames, fnames, signature)
    unRematchDefinition(definition)

    asMethodDefinition(def, signature, sealed = FALSE, fdef)

    addNextMethod(method, f, mlist, optional, envir)

    insertClassMethods(methods, Class, value, fieldNames, returnAll)

### Summary of Functions

`getGeneric`:

  returns the definition of the function named `f` as a generic.

  If no definition is found, throws an error or returns `NULL` according to the value of `mustFind`. By default, searches in the top-level environment (normally the global environment, but adjusted to work correctly when package code is evaluated from the function `library`).

  Primitive functions are dealt with specially, since there is never a formal generic definition for them. The value returned is the formal definition used for assigning methods to this primitive. Not all primitives can have methods; if this one can't, then `getGeneric` returns `NULL` or throws an error.

`getGroup`:

  returns the groups to which this generic belongs, searching from environment `where` (the global environment normally by default).

  If `recursive=TRUE`, also all the group(s) of these groups.

`getGroupMembers`:

  Return all the members of the group generic function named `group`. If `recursive` is `TRUE`, and some members are group generics, includes their members as well. If `character` is `TRUE`, returns just a character vector of the names; otherwise returns a list, whose elements may (or may not) include either names with a package attribute or actual generic functions.

  Note that members that are not defined as generic functions will not be included in the returned value. To see the raw data, use `getGeneric(group)@groupMembers`.

`getMethodsMetaData`, `assignMethodsMetaData`, `mlistMetaName`:

  Utilities to get (`getMethodsMetaData`) and assign (`assignMethodsMetaData`) the metadata object recording the methods defined in a particular package, or to return the mangled name for that object (`mlistMetaName`).

  The assign function should not be used directly. The get function may be useful if you want explicitly only the outcome of the methods assigned in this package. Otherwise, use `getMethods`.

`matchSignature`:

  Matches the signature object (a partially or completely named subset of the signature arguments of the generic function object `fun`), and return a vector of all the classes in the order specified by `fun@signature`. The classes not specified by `signature` will be `"ANY"` in the value, but extra trailing `"ANY"`'s are removed. When the input signature is empty, the returned signature is a single `"ANY"` matching the first formal argument (so the returned value is always non-empty).

  Generates an error if any of the supplied signature names are not legal; that is, not in the signature slot of the generic function.

  If argument `where` is supplied, a warning will be issued if any of the classes does not have a formal definition visible from `where`.

`MethodAddCoerce`:

  Possibly modify one or more methods to explicitly coerce this argument to `methodClass`, the class for which the method is explicitly defined. Only modifies the method if an explicit coerce is required to coerce from `thisClass` to `methodClass`.

`findUnique`:

  Return the list of environments (or equivalent) having an object named `what`, using environment `where` and its parent environments. If more than one is found, a warning message is generated, using `message` to identify what was being searched for, unless `message` is the empty string.

`cacheMetaData`, `cacheGenericsMetaData`, `setPrimitiveMethods`:

  Utilities for ensuring that the internal information about class and method definitions is up to date. Should normally be called automatically whenever needed (for example, when a method or class definition changes, or when a package is attached or detached). Required primarily because primitive functions are dispatched in C code, rather than by the official model.

  The `setPrimitiveMethods` function resets the caching information for a particular primitive function. Don't call it directly.

`missingArg`:

  Returns `TRUE` if the symbol supplied is missing from the call corresponding to the environment supplied (by default, environment of the call to `missingArg`). If `eval` is true, the argument is evaluated to get the name of the symbol to test. Note that `missingArg` is closer to the ‘Blue Book’ sense of the `missing` function, not that of the current R base package implementation. But beware that it works reliably only if no assignment has yet been made to the argument. (For method dispatch this is fine, because computations are done at the beginning of the call.)

`balanceMethodsList`:

  Called from `setMethod` to ensure that all nodes in the list have the same depth (i.e., the same number of levels of arguments). Balance is needed to ensure that all necessary arguments are examined when inherited methods are being found and added to the `allMethods` slot. No actual recomputation is needed usually except when a new method uses a longer signature than has appeared before.

  Balance requires that all methods be added to the generic via `setMethod` (how else could you do it?) or by the initial `setGeneric` call converting the ordinary function.

`sigToEnv`:

  Turn the signature (a named vector of classes) into an environment with the classes assigned to the names. The environment is then suitable for calling `MethodsListSelect`, with `evalArgs=FALSE`, to select a method corresponding to the signature. Usually not called directly: see `selectMethod`.

`.saveImage`:

  Flag, used in dynamically initializing the methods package from `.onLoad`.

`rematchDefinition`, `unRematchDefinition`:

  If the specified method in a call to `setMethod` specializes the argument list (by replacing ...), then `rematchDefinition` constructs the actual method stored. Using knowledge of how `rematchDefinition` works, `unRematchDefinition` reverses the procedure; if given a function or method definition that does not correspond to this form, it just returns its argument.

`asMethodDefinition`:

  Turn a function definition into an object of class `MethodDefinition`, corresponding to the given `signature` (by default generates a default method with empty signature). The definition is sealed according to the `sealed` argument.

`addNextMethod`:

  A generic function that finds the next method for the signature of the method definition `method` and caches that method in the method definition (promoting the class to `"MethodWithNext"`. Note that argument `mlist` is obsolete and not used.

`makeGeneric`:

  Makes a generic function object corresponding to the given function name, optional definition and optional default method. Other arguments supply optional elements for the slots of class `genericFunction`.

`makeStandardGeneric`:

  a utility function that makes a valid function calling `standardGeneric` for name `f`. Works (more or less) even if the actual definition, `fdef`, is not a proper function, that is, it's a primitive or internal.

`conformMethod`:

  If the formal arguments, `mnames`, are not identical to the formal arguments to the function, `fnames`, `conformMethod` determines whether the signature and the two sets of arguments conform, and returns the signature, possibly extended. The function name, `f` is supplied for error messages. The generic function, `fdef`, supplies the generic signature for matching purposes.

  The method assignment conforms if method and generic function have identical formal argument lists. It can also conform if the method omits some of the formal arguments of the function but: (1) the non-omitted arguments are a subset of the function arguments, appearing in the same order; (2) there are no arguments to the method that are not arguments to the function; and (3) the omitted formal arguments do not appear as explicit classes in the signature. A future extension hopes to test also that the omitted arguments are not assumed by being used as locally assigned names or function names in the body of the method.

`defaultDumpName`:

  the default name to be used for dumping a method.

`doPrimitiveMethod`:

  do a primitive call to builtin function `name` the definition and call provided, and carried out in the environment `ev`.

  A call to `doPrimitiveMethod` is used when the actual method is a .Primitive. (Because primitives don't behave correctly as ordinary functions, not having either formal arguments nor a function body).

### See Also

`setGeneric`, `setClass`, `showMethods`.

### Examples

    getGroup("exp")
    getGroup("==", recursive = TRUE)

    getGroupMembers("Arith")
    getGroupMembers("Math")
    getGroupMembers("Ops") # -> its sub groups

[Package methods version 3.1.2 Index]