Register an S7, S3, or union class with S4

If you want to use method<- to register a method for an S4 generic with an S7 class that does not extend an S4 class, or an S3 class created by new_S3_class(), you need to call S4_register() once. Classes created by new_class() with an S4 parent are registered automatically.

Usage

S4_register(class, env = parent.frame())

S4_contains(class, env = parent.frame())

Arguments

class: An S7 class created with new_class(), or, for S4_register() only, an S3 class created with new_S3_class() or an S7 union created with new_union().
env: Expert use only. Environment where S4 class will be registered.

Value

Called for its side effects and invisibly returns the registered S4 class name.

Details

S4_register() registers an S7 class, S3 class, or S7 union with S4 and invisibly returns the registered S4 class name. For S7 classes, this creates a virtual S4 old class that exposes stored S7 properties as S4 slots and carries the _S7_class slot needed for S7 dispatch and validation.

After registration, S4_contains() returns the virtual S4 class name to use when an S4 class should extend an S7 class with methods::setClass(contains = ). It asserts that the S7 properties can safely cross the S4 inheritance boundary.

Register S7 unions with S4_register() before using them in S4 slots or method signatures unless an equivalent S4 union already exists.

See vignette("compatibility") for examples and caveats.

Examples

methods::setGeneric("S4_generic", function(x) {
  standardGeneric("S4_generic")
})
#> [1] "S4_generic"

Foo := new_class()
S4_register(Foo)
method(S4_generic, Foo) <- function(x) "Hello"

S4_generic(Foo())
#> [1] "Hello"

S4Foo := new_class(properties = list(x = class_numeric), package = "S7")
S4_register(S4Foo)
S4Foo_S4 <- S4_contains(S4Foo)
methods::setClass("S4Child", contains = S4Foo_S4)