setRcppClass: Create a Class Extending a C++ Class

In jjallaire/Rcpp: Seamless R and C++ Integration

Description

A class is defined that includes the fields and methods of a C++ class defined, usually in this package. The R class can include new methods and fields, such as for prototyping new computations for the C++ class.

Usage

setRcppClass(Class, CppClass, module, fields = list(), contains = , methods = , saveAs = Class, where = , ...)

Arguments

Class	The name for the new class.
CppClass	The C++ class defined in the C++ code for the package that this class extends. By default, the same as Class.
module	The Rcpp module in which the class is defined. The module does not have to be loaded separately; setRcppClass() will arrange to load the module.
fields, contains, methods	Additional fields, superclasses and method definitions in R that extend the C++ class. These arguments are passed on to setRefClass(). See Details for the implementation of methods.
saveAs	Save a generator object for the class in the package's namespace under this name. By default, the generator object has the name of the class. To avoid saving any generator object, supply this argument as NULL.
where	The environment in which to save the class definition. By default, will be the namespace of the package in which the setRcppClass() call is included.
...	Arguments, if any, to pass on to setRefClass().

Details

The call to this function normally appears in the source code for a package. It generates a load action that loads the specified module and extracts the C++ class definition specified.

R code can define new fields and methods for the class, typically as prototypes for possible future C++ implementation. Methods for the R class can refer to methods and fields defined in C++ for the C++ class. These will be mapped into the C++ equivalents by R code generated by setRcppClass. The C++ code may not deal as well as R with incompatible argument types and lengths. Segmentation faults are a definite possibility. If that's a problem, you should define methods in R that check for legal data types and values.

The fields and methods defined can include overriding C++ fields or methods. Keep in mind, however, that R methods can refer to C++ fields and methods, but not the reverse. If you override a C++ field or method, you essentially need to revise all code that refers to that field or method. Otherwise, the C++ code will continue to use the old C++ definition.

Value

A generator for the new class.

Note

This function and function loadModule() require version 2.15.0 of R or later, in order to use load actions, introduced in that version.

A subtle way this can fail is by somehow loading a legitimate binary version of your package (installed under a valid version of R) into a session with an older R. In this case the load actions created in the binary package will simply not be called. None of the modules will be loaded and none of the classes created.

If your symptom is that classes or other objects from modules don't exist, check the R version.

Author(s)

John Chambers

Examples

## Not run: 
setRcppClass("World", 
    module = "yada", 
    fields = list(more = "character"),
    methods = list(
        test = function(what) message("Testing: ", what, "; ", more)),
    saveAs = "genWorld"
         )

## End(Not run)

jjallaire/Rcpp documentation built on May 19, 2019, 11:37 a.m.