# nocov start
.onLoad <- function(libname, pkgname){
pkg_env = asNamespace(pkgname)
# S4 method is hard and so far this is the best way to do it
# We detect if pkg is installed,
# if so, import generic from pkg, add methods and export
# if not, define generics, add methods and export
register_generics <- function(pkg, generic, signature, fun = NULL){
stopifnot(is.character(pkg), length(pkg) == 1)
stopifnot(is.character(generic), length(generic) == 1)
if (is.null(fun)) {
fun <- get(generic, envir = parent.frame())
} else if(is.character(fun)){
fun <- get(fun, envir = parent.frame())
} else {
stopifnot(is.function(fun))
}
if(!is.list(signature)){
signature = list(signature)
}
# Check if pkg has been installed
if(system.file('', package = pkg) != ''){
# installed, extend the definition
register <- function(...){
tmp_env = new.env()
base::namespaceImportFrom(self = tmp_env, ns = pkg, generic)
for(sig in signature){
methods::setMethod(f = generic, signature = sig, definition = fun, where = tmp_env)
}
# Need to override the definition
pkg_env[[generic]] = tmp_env[[generic]]
base::namespaceExport(pkg_env, generic)
}
}else{
register <- function(...){
assign(generic, methods::makeGeneric(generic, fun), envir = pkg_env)
for(sig in signature){
methods::setMethod(f = generic, signature = sig, definition = fun, where = pkg_env)
}
base::namespaceExport(pkg_env, generic)
}
}
register()
}
register_generics('Matrix', '%&%', signature = list(
methods::signature(x = "character", y = 'ANY'),
methods::signature(x = "ANY", y = 'character'),
methods::signature(x = "character", y = 'character')
))
invisible()
}
# S3 method is easy because I can dynamically update S3 table
register_s3_method <- function(pkg, generic, class, fun = NULL) {
stopifnot(is.character(pkg), length(pkg) == 1)
stopifnot(is.character(generic), length(generic) == 1)
stopifnot(is.character(class), length(class) == 1)
if (is.null(fun)) {
fun <- get(paste0(generic, ".", class), envir = parent.frame())
} else if(is.character(fun)){
fun <- get(fun, envir = parent.frame())
} else {
stopifnot(is.function(fun))
}
if (pkg %in% loadedNamespaces()) {
registerS3method(generic, class, fun, envir = asNamespace(pkg))
}
# Always register hook in case package is later unloaded & reloaded
setHook(
packageEvent(pkg, "onLoad"),
function(...) {
registerS3method(generic, class, fun, envir = asNamespace(pkg))
}
)
}
# nocov end
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