责任链模式
正文：https://refactoringguru.cn/design-patterns/chain-of-responsibility
Go代码：https://refactoringguru.cn/design-patterns/chain-of-responsibility/go/example
示例
本例子模拟医院的看病缴费的责任链。
病人需要进行的大致步骤是：
- 进院，注册信息
- 医生检查
- 药房给药
- 病人缴费，出院
!> CoR: Hospital departments
module hospital_CoR
implicit none
private
public :: patient_type, department_type, reception_type, doctor_type, medical_type, cashier_type
type patient_type
character(:), allocatable :: name
logical :: registration_done
logical :: doctor_check_up_done
logical :: medicine_done
logical :: payment_done
end type patient_type
type, abstract :: department_type
contains
procedure(execute_procedure), deferred :: execute
procedure(set_next_procedure), deferred :: set_next
end type department_type
abstract interface
subroutine execute_procedure(self, p)
import department_type, patient_type
class(department_type), intent(inout) :: self
type(patient_type), intent(inout) :: p
end subroutine execute_procedure
subroutine set_next_procedure(self, next)
import department_type
class(department_type), intent(inout) :: self
class(department_type), intent(inout) :: next
end subroutine set_next_procedure
end interface
type, extends(department_type) :: reception_type
class(department_type), pointer :: next
contains
procedure :: execute => reception_type_execute
procedure :: set_next => reception_type_set_next
end type reception_type
type, extends(department_type) :: doctor_type
class(department_type), pointer :: next
contains
procedure :: execute => doctor_type_execute
procedure :: set_next => doctor_type_set_next
end type doctor_type
type, extends(department_type) :: medical_type
class(department_type), pointer :: next
contains
procedure :: execute => medicine_type_execute
procedure :: set_next => medicine_type_set_next
end type medical_type
type, extends(department_type) :: cashier_type
class(department_type), pointer :: next
contains
procedure :: execute => cashier_type_execute
procedure :: set_next => cashier_type_set_next
end type cashier_type
contains
subroutine reception_type_execute(self, p)
class(reception_type), intent(inout) :: self
type(patient_type), intent(inout) :: p
if (p%registration_done) then
print *, "Patient registration already done.✔️"
call self%next%execute(p)
return
end if
print *, "Reception registering patient."
p%registration_done = .true.
call self%next%execute(p)
end subroutine reception_type_execute
subroutine reception_type_set_next(self, next)
class(reception_type), intent(inout) :: self
class(department_type), intent(inout) :: next
allocate (self%next, source=next)
end subroutine reception_type_set_next
subroutine doctor_type_execute(self, p)
class(doctor_type), intent(inout) :: self
type(patient_type), intent(inout) :: p
if (p%doctor_check_up_done) then
print *, "Doctor checkup already done.✔️"
call self%next%execute(p)
return
end if
print *, "Doctor checking patient."
p%doctor_check_up_done = .true.
call self%next%execute(p)
end subroutine doctor_type_execute
subroutine doctor_type_set_next(self, next)
class(doctor_type), intent(inout) :: self
class(department_type), intent(inout) :: next
allocate (self%next, source=next)
end subroutine doctor_type_set_next
subroutine medicine_type_execute(self, p)
class(medical_type), intent(inout) :: self
type(patient_type), intent(inout) :: p
if (p%medicine_done) then
print *, "Medicine already given to patient.✔️"
call self%next%execute(p)
return
end if
print *, "Medical giving medicine to patient."
p%medicine_done = .true.
call self%next%execute(p)
end subroutine medicine_type_execute
subroutine medicine_type_set_next(self, next)
class(medical_type), intent(inout) :: self
class(department_type), intent(inout) :: next
allocate (self%next, source=next)
end subroutine medicine_type_set_next
subroutine cashier_type_execute(self, p)
class(cashier_type), intent(inout) :: self
type(patient_type), intent(inout) :: p
if (p%payment_done) then
print *, "Payment Done.✔️"
return
end if
print *, "Cashier getting money from patient."
p%payment_done = .true.
end subroutine cashier_type_execute
subroutine cashier_type_set_next(self, next)
class(cashier_type), intent(inout) :: self
class(department_type), intent(inout) :: next
allocate (self%next, source=next)
end subroutine cashier_type_set_next
end module hospital_CoR
!> CoR: Patient visiting hospital
program CoR_main
use hospital_CoR
type(cashier_type) :: c
type(medical_type) :: m
type(doctor_type) :: d
type(reception_type) :: r
type(patient_type) :: p1, p2
!> Set next for departments
call m%set_next(c)
call d%set_next(m)
call r%set_next(d)
p1 = patient_type("abc", .true., .true., .true., .true.)
!> Patient visiting
print *, "> Patient `"//p1%name//"` : "
call r%execute(p1)
p2 = patient_type("def", .true., .false., .false., .false.)
!> Patient visiting
print *, "> Patient `"//p2%name//"` : "
call r%execute(p2)
!> Optional statements
deallocate (m%next)
deallocate (d%next)
deallocate (r%next)
end program CoR_main
!> Results shall be:
! > Patient `abc` :
! Patient registration already done.✔️
! Doctor checkup already done.✔️
! Medicine already given to patient.✔️
! Payment Done.✔️
! > Patient `def` :
! Patient registration already done.✔️
! Doctor checking patient.
! Medical giving medicine to patient.
! Cashier getting money from patient.
评价
责任链很像流水线，上一节点处理完进入下一节点。
可以应用于科学计算的文件输入检查过程。