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jeremybenn |
! { dg-do compile }
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!
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! PR fortran/51995
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!
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! Contributed by jilfa12@yahoo.com
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!
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MODULE factory_pattern
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TYPE CFactory
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PRIVATE
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CHARACTER(len=20) :: factory_type !! Descriptive name for database
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CLASS(Connection), POINTER :: connection_type !! Which type of database ?
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CONTAINS !! Note 'class' not 'type' !
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PROCEDURE :: init !! Constructor
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PROCEDURE :: create_connection !! Connect to database
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PROCEDURE :: finalize !! Destructor
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END TYPE CFactory
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TYPE, ABSTRACT :: Connection
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CONTAINS
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PROCEDURE(generic_desc), DEFERRED, PASS(self) :: description
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END TYPE Connection
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ABSTRACT INTERFACE
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SUBROUTINE generic_desc(self)
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IMPORT :: Connection
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CLASS(Connection), INTENT(in) :: self
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END SUBROUTINE generic_desc
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END INTERFACE
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!! An Oracle connection
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TYPE, EXTENDS(Connection) :: OracleConnection
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CONTAINS
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PROCEDURE, PASS(self) :: description => oracle_desc
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END TYPE OracleConnection
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!! A MySQL connection
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TYPE, EXTENDS(Connection) :: MySQLConnection
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CONTAINS
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PROCEDURE, PASS(self) :: description => mysql_desc
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END TYPE MySQLConnection
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CONTAINS
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SUBROUTINE init(self, string)
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CLASS(CFactory), INTENT(inout) :: self
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CHARACTER(len=*), INTENT(in) :: string
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self%factory_type = TRIM(string)
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self%connection_type => NULL() !! pointer is nullified
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END SUBROUTINE init
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SUBROUTINE finalize(self)
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CLASS(CFactory), INTENT(inout) :: self
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DEALLOCATE(self%connection_type) !! Free the memory
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NULLIFY(self%connection_type)
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END SUBROUTINE finalize
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FUNCTION create_connection(self) RESULT(ptr)
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CLASS(CFactory) :: self
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CLASS(Connection), POINTER :: ptr
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IF(self%factory_type == "Oracle") THEN
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IF(ASSOCIATED(self%connection_type)) DEALLOCATE(self%connection_type)
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ALLOCATE(OracleConnection :: self%connection_type)
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ptr => self%connection_type
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ELSEIF(self%factory_type == "MySQL") THEN
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IF(ASSOCIATED(self%connection_type)) DEALLOCATE(self%connection_type)
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ALLOCATE(MySQLConnection :: self%connection_type)
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ptr => self%connection_type
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END IF
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END FUNCTION create_connection
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SUBROUTINE oracle_desc(self)
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CLASS(OracleConnection), INTENT(in) :: self
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WRITE(*,'(A)') "You are now connected with Oracle"
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END SUBROUTINE oracle_desc
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SUBROUTINE mysql_desc(self)
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CLASS(MySQLConnection), INTENT(in) :: self
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WRITE(*,'(A)') "You are now connected with MySQL"
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END SUBROUTINE mysql_desc
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end module
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PROGRAM main
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USE factory_pattern
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IMPLICIT NONE
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TYPE(CFactory) :: factory
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CLASS(Connection), POINTER :: db_connect => NULL()
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CALL factory%init("Oracle")
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db_connect => factory%create_connection() !! Create Oracle DB
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CALL db_connect%description()
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!! The same factory can be used to create different connections
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CALL factory%init("MySQL") !! Create MySQL DB
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!! 'connect' is a 'class' pointer. So can be used for either Oracle or MySQL
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db_connect => factory%create_connection()
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CALL db_connect%description()
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CALL factory%finalize() ! Destroy the object
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END PROGRAM main
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! { dg-final { cleanup-modules "factory_pattern" } }
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