R/util-make_class_optional.R

In RDocTaskForce/extendedRef: Reference Classes with Static and Private Variables

#' Convert a normal class into an optional class.
#'
#' This will create a new class based off the given class
#' where NULL is an acceptable value for the given entry.
#' This creates a new class so that both the original and
#' the optional version may be used.
#'
#' @param className the class to make optional
#' @param name the name of the resulting class union
#' @param where where to save the new class definition
#'
make_class_optional <-
function( className
        , name = paste0('optional-', className)
        , where = topenv(parent.frame())
        ){
    setClassUnion(name, className, where=where)
    setIs('NULL', name, where=where)
}
if(FALSE){#@testing
    if (exists(classMetaName('test'), where=globalenv()))
        removeClass('test', where=globalenv())
    new_test <- setClass('test', representation = list(a='logical'), where=globalenv())
    make_class_optional('test', 'optional-test', where=globalenv())

    expect_true(exists(classMetaName('optional-test'), where=globalenv()))

    expect_true(is(NULL, 'optional-test'))

    expect_is(x <- new_test(a=TRUE), 'test')
    expect_true(is(x, 'optional-test'))

    expect_true(removeClass('optional-test', where=globalenv()))
    expect_true(removeClass('test', where=globalenv()))
}