fortran - 现代 Fortran : Calling an ancestor procedure from descendent

Question

我开始使用现代 Fortran 的面向对象功能，并且已经熟悉其他语言的面向对象。在 Delphi (Object Pascal) 中，通常会在其覆盖的后代过程中调用过程的祖先版本，甚至有一个“继承”的语言语句允许这样做。我找不到等效的 Fortran 构造 - 但可能正在寻找错误的东西。请参阅下面的简单示例。非常感谢任何建议。

type tClass
  integer :: i
contains
  procedure Clear => Clear_Class
end type tClass

type tSubClass
  integer :: j
contains
  procedure Clear => Clear_SubClass
end type tSubClass

subroutine Clear_Class
  i = 0
end subroutine

subroutine Clear_SubClass
  inherited Clear ! this is the Delphi way
  j = 0
end subroutine

Answer 1

下面是一些示例代码，尝试通过@HighPerformanceMark 实现注释(即，子类型具有引用父类型的隐藏组件)。

module testmod
    implicit none

    type tClass
        integer :: i = 123
    contains
        procedure :: Clear => Clear_Class
    endtype

    type, extends(tClass) :: tSubClass
        integer :: j = 456
    contains
        procedure :: Clear => Clear_SubClass
    endtype

contains

    subroutine Clear_Class( this )
        class(tClass) :: this
        this % i = 0
    end

    subroutine Clear_SubClass( this )
        class(tSubClass) :: this
        this % j = 0
        call this % tClass % Clear()  !! (*) calling a method of the parent type
    end
end

program main
    use testmod
    implicit none
    type(tClass) :: foo
    type(tSubClass) :: subfoo

    print *, "foo (before) = ", foo
    call foo % Clear()
    print *, "foo (after)  = ", foo

    print *, "subfoo (before) = ", subfoo
    call subfoo % Clear()
    print *, "subfoo (after)  = ", subfoo
end

给出(使用 gfortran-8.2)

 foo (before) =          123
 foo (after)  =            0
 subfoo (before) =          123         456
 subfoo (after)  =            0           0

如果我们注释掉标有 (*) 的行，subfoo % i 将保持不变:

 foo (before) =          123
 foo (after)  =            0
 subfoo (before) =          123         456
 subfoo (after)  =          123           0