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Explain method dispatch

Source: R/method-introspect.R
method_explain.Rd

method_explain() shows all possible methods that a call to a generic might use, which ones exist, and which one will actually be called.

Note that method dispatch uses a string representation of each class in the class hierarchy. Each class system uses a slightly different convention to avoid ambiguity.

  • S7: pkg::class or class

  • S4: S4/pkg::class or S4/class

  • S3: class

Usage

method_explain(generic, class = NULL, object = NULL)

Arguments

generic

An S7 generic, i.e. the result of new_generic(). Unlike method<-, method() only works with S7 generics; it does not look up methods registered on S3 or S4 generics.

class, object

Perform introspection either with a class (processed with as_class()) or a concrete object. If generic uses multiple dispatch then both object and class must be a list of classes/objects.

Value

Nothing; this function is called for it's side effects.

Examples

Foo1 := new_class()
Foo2 := new_class(Foo1)

add := new_generic(c("x", "y"))
method(add, list(Foo2, Foo1)) <- function(x, y) c(2, 1)
method(add, list(Foo1, Foo1)) <- function(x, y) c(1, 1)

method_explain(add, list(Foo2, Foo2))
#>    add([Foo2], [Foo2])
#> -> add([Foo2], [Foo1])
#>    add([Foo2], [S7_object])
#>    add([Foo2], [ANY])
#>    add([Foo1], [Foo2])
#> *  add([Foo1], [Foo1])
#>    add([Foo1], [S7_object])
#>    add([Foo1], [ANY])
#>    add([S7_object], [Foo2])
#>    add([S7_object], [Foo1])
#>    add([S7_object], [S7_object])
#>    add([S7_object], [ANY])
#>    add([ANY], [Foo2])
#>    add([ANY], [Foo1])
#>    add([ANY], [S7_object])
#>    add([ANY], [ANY])