Vícenásobné úrovně dědičnosti

Objektově orientované programování s S3 a R6 v R

Richie Cotton

Data Evangelist at DataCamp

ch4_3-multiple-levels-of-inheritance.003.png

ch4_3-multiple-levels-of-inheritance.005.png

ch4_3-multiple-levels-of-inheritance.006.png

thing_factory <- R6Class(
  "Thing"
)

child_thing_factory <- R6Class(
  "ChildThing",
  inherit = thing_factory
)

grand_child_thing_factory <- R6Class(
  "GrandChildThing",
  inherit = child_thing_factory
)

thing_factory <- R6Class(
  "Thing",

  public = list(
    do_something = function() {
      message("the parent do_something method")
    }
  )

)

child_thing_factory <- R6Class(
  "ChildThing",
  inherit = thing_factory,

  public = list(
    do_something = function() {
      message("the child do_something method")
    }
  )

)

grand_child_thing_factory <- R6Class(
  "GrandChildThing",
  inherit = child_thing_factory,
  public = list(
    do_something = function() {
      message("the grand-child do_something method")

      super$do_something()

      super$super$do_something()

    }
  )
)

a_grand_child_thing <- grand_child_thing_factory$new()

a_grand_child_thing$do_something()

the grand-child do_something method

the child do_something method

Error in a_grand_child_thing$do_something(): 
  attempt to apply non-function

child_thing_factory <- R6Class(
  "ChildThing",
  inherit = thing_factory,
  public = list(
    do_something = function() {
      message("the child do_something method")
    }
  ),

  active = list(
    super_ = function() super
  )

)

grand_child_thing_factory <- R6Class(
  "GrandChildThing",
  inherit = child_thing_factory,
  public = list(
    do_something = function() {
      message("the grand-child do_something method")

      super$do_something()

      super$super_$do_something()

    }
  )
)

a_grand_child_thing <- grand_child_thing_factory$new()

a_grand_child_thing$do_something()

the grand-child do_something method
the child do_something method
the parent do_something method

Shrnutí

R6 objekty mají přístup pouze k přímému rodiči
Mezilehlé třídy mohou zpřístupnit svého rodiče
Použijte aktivní vazbu s názvem super_
super_ má jednoduše vracet super

Pojďme si procvičit!

Objektově orientované programování s S3 a R6 v R