我想调用一个重写的 PL/SQL 方法.举个例子:
I'd like to call an overridden PL/SQL method. Here's an example:
-- super class
create or replace type test as object
(
n number,
member procedure proc(SELF in out nocopy test, s varchar2)
)
alter type test not final
/
create or replace type body test is
member procedure proc(SELF in out nocopy test, s varchar2) is
begin
dbms_output.put_line('test1: n='||nvl(self.n, 'null')||' s='||s);
self.n := to_number(s);
end;
end;
/
-- derived class
create or replace type test2 under test
(
overriding member procedure proc(SELF in out nocopy test2, s varchar2)
)
/
现在我想调用 proc
方法的继承版本.当我尝试执行像 treat(self as test).proc(s);
这样的显式转换时,它不会编译,因为 PLS-00363: expression 'SYS_TREAT' cannot be used as分配目标
Now I want to invoke the inherited version of the proc
method. When I try to do an explicit cast like treat(self as test).proc(s);
it won't compile because of PLS-00363: expression 'SYS_TREAT' cannot be used as an assignment target
类型主体在我使用局部变量时编译:
The type body compiles when I use a local variable:
create or replace type body test2 is
overriding member procedure proc(SELF in out nocopy test2, s varchar2) is
O test;
begin
O := treat(self as test);
O.proc(s);
end;
end;
/
但是当我像这样运行我的例子时
But when I run my example like this
declare
obj test2;
begin
obj := test2(0);
obj.proc('1');
end;
...它抛出ORA-21780:超出对象持续时间的最大数量.
有什么方法可以调用 test::proc(无需序列化/反序列化)?
Is there any way to call test::proc (without serializing/deserializing)?
而且...在proc被调用后,如何在obj
中反映任何改变的属性(即n
)?
And... after proc has been called, how can any changed attributes (namely n
) be reflected in obj
?
更新(谢谢,tbone):
Update (Thanks, tbone):
我使用模板方法(之前"和之后")更改了我的方法的组织.每当我需要扩展方法时,我都会添加它们.
I changed the organization of my methods using template methods ('before' and 'after'). I add them whenever I need to extend a method.
create or replace type test as object
(
n number,
member procedure proc (SELF in out nocopy test, s varchar2),
member procedure afterProc (SELF in out nocopy test, s varchar2)
member procedure beforeProc(SELF in out nocopy test, s varchar2),
)
not final
/
create or replace type body test is
member procedure proc(SELF in out nocopy test, s varchar2) is
begin
beforeProc(s);
dbms_output.put_line('test1: n='||nvl(n, 'null')||' s='||s);
n := to_number(s);
afterProc(s);
end;
member procedure afterProc (SELF in out nocopy test, s varchar2) is begin null; end;
member procedure beforeProc(SELF in out nocopy test, s varchar2) is begin null; end;
end;
/
要访问超级方法,请尝试通用调用或通用表达式.例如,使用个人超类型和学生子类型:
To access the super methods, try either general invocation or generalized expression. For example, using a person supertype and student subtype:
CREATE OR REPLACE TYPE person_typ AS OBJECT (
idno number,
name varchar2(30),
phone varchar2(20),
MAP MEMBER FUNCTION get_idno RETURN NUMBER,
MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE OR REPLACE TYPE BODY person_typ AS
MAP MEMBER FUNCTION get_idno RETURN NUMBER IS
BEGIN
RETURN idno;
END;
MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
-- function that can be overriden by subtypes MEMBER FUNCTION show RETURN VARCHAR2 IS BEGIN
RETURN 'Id: ' || TO_CHAR(idno) || ', Name: ' || name;
END;
END;
CREATE TYPE student_typ UNDER person_typ (
dept_id NUMBER,
major VARCHAR2(30),
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE TYPE BODY student_typ AS
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN (self AS person_typ).show || ' -- Major: ' || major ;
END;
END;
-- Using Generalized Invocation
DECLARE
myvar student_typ := student_typ(100, 'Sam', '6505556666', 100, 'Math');
name VARCHAR2(100);
BEGIN
name := (myvar AS person_typ).show; --Generalized invocation
END;
-- Using Generalized Expression
DECLARE
myvar2 student_typ := student_typ(101, 'Sam', '6505556666', 100, 'Math');
name2 VARCHAR2(100);
BEGIN
name2 := person_typ.show((myvar2 AS person_typ)); -- Generalized expression
END;
如果您使用的是 10g,则需要对函数进行一些不同的组织,但与调用 super 方法的子函数具有相同的功能:
If you are on 10g, you'll need to organize the functions a bit different, but same functionality from the child to call the super method:
CREATE TYPE BODY person_typ AS
MAP MEMBER FUNCTION get_idno RETURN NUMBER IS
BEGIN
RETURN idno;
END;
-- static function that can be called by subtypes
STATIC FUNCTION show_super (person_obj in person_typ) RETURN VARCHAR2 IS
BEGIN
RETURN 'Id: ' || TO_CHAR(person_obj.idno) || ', Name: ' || person_obj.name;
END;
-- function that can be overriden by subtypes
MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN person_typ.show_super ( SELF );
END;
END;
CREATE TYPE student_typ UNDER person_typ (
dept_id NUMBER,
major VARCHAR2(30),
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2)
NOT FINAL;
CREATE TYPE BODY student_typ AS
OVERRIDING MEMBER FUNCTION show RETURN VARCHAR2 IS
BEGIN
RETURN person_typ.show_super ( SELF ) || ' -- Major: ' || major ;
END;
END;
现在您可以从 student 中为 person 方法调用 show_super(),或者为 student 方法调用 show().
Now you'd call show_super() from student for the person method, or just show() for the student method.
来自文档,希望有所帮助.
From the docs, hope that helps.
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