紧急求助仙子,怎么判断函数指针的有效性

qnxchina

原始需求如下:
需要写一个测试框架接口,其中需要在测试结束后完成后处理工作,公共接口模板部分在测试用例执行前和用户代码拼接成一个完整的PL,
公共接口模板部分需要判断用户自己写的代码中是否存在一个特定名称的函数,有则执行,没有则忽略

现在解决方法是,模板接口代码取后处理函数的指针,然后判断指针是否有效来决定是否调用,但是defined无法判断该指针是否有效,如何解决??

qnxchina

突然间发现,暴力的直接调用就可以了,如果不存在就会当作一个字符串常量的引用
不过难道就没个幽雅点的方法么?

climby

如下的判断方法可以么？

1. 
   
2. if (defined(&{$func_ref}) {
   
3.     &{$func_ref}};
   
4.     print $@ if $@;
   
5. }
   
6. else {
   
7.     print function does not exist\n";
   
8. }
   
9. 
   

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climby

对我刚才的回复稍加了修改，希望能满足你的要求：

1. 
   
2. #!/usr/bin/perl
   
3. 
   
4. sub func1 {
   
5.     print "func1 is running\n";
   
6. }
   
7. 
   
8. sub func_test {
   
9.     my $func_ref = shift;
   
10. 
    
11.     # ref will return 'CODE' if it's function reference
    
12.     if ( ( ref($func_ref) eq "CODE" )
    
13.         && defined( &{$func_ref} ) )
    
14.     {
    
15.         &{$func_ref};
    
16.         print $@ if $@;
    
17.     }
    
18.     else {
    
19.         print "Not real function was called! \n";
    
20.     }
    
21. }
    
22. 
    
23. ## testing from here
    
24. my $func_ref = \&func1;
    
25. my $anoy_ref = sub { print "anonymous function is running\n" };
    
26. my $var      = "abcd";
    
27. my $var_ref  = \$var;
    
28. 
    
29. func_test($func_ref);
    
30. func_test($anoy_ref);
    
31. func_test($var);
    
32. func_test($var_ref)
    
33. 
    
34. 
    

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测试结果输出：

1. 
   
2. func1 is running
   
3. anonymous function is running
   
4. Not real function was called!
   
5. Not real function was called!
   

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qnxchina

我是用的比较暴力的方法,只要调用的函数在调用代码之前定义,并且去掉use strict "subs";

my $cleanup_func_ref;
$cleanup_func_ref=\cleanup_func;
$$cleanup_func_ref;

不过这样就需要使用者在写函数时要小心点了

qnxchina

算了,还是用你的方法吧,毕竟破坏strict不是好方法

兰花仙子

Package::Name->can('function')

or

*Package::Name::function{CODE}

# or no strict; *{ "Package::Name::$function" }{CODE}

or just live with the exception. If you call the function in an eval and $@ is set, then you can't call the function.

Finally, it sounds like you may want Test::Class instead of writing this yourself.

nuclearxin

Package::Name->can('function')

or

*Package::Name::function{CODE}

# or no strict; *{ &quotackag ...
兰花仙子 发表于 2010-05-28 18:51

    Package::Name->can('function')

can 这个method 是perl 提供的吗?

dugu072_cu

回复 8# nuclearxin


    那是由于Perl 在所有类的 @ISA 末尾添加了一个 UNIVERSAL 的Class, 该类提供 can()

nuclearxin

回复 9# dugu072_cu


    3q
看到了

1. 
   
2. 
   
3. When you invoke a method methname on an invocant of type classname, Perl tries six different ways to find a subroutine to use:
   
4. 
   
5. First, Perl looks in the invocant's own package for a subroutine named classname::methname. If that fails, inheritance kicks in, and we go to step 2.
   
6. 
   
7. Next, Perl checks for methods inherited from base classes by looking in all parent packages listed in @classname::ISA for a parent::methname subroutine. The search is left-to-right, recursive, and depth-first. The recursion assures that grandparent classes, great-grandparent classes, great-great-grandparent classes, and so on, are all searched.
   
8. 
   
9. If that fails, Perl looks for a subroutine named UNIVERSAL::methname.
   
10. 
    
11. At this point, Perl gives up on methname and starts looking for an AUTOLOAD. First, it looks for a subroutine named classname::AUTOLOAD.
    
12. 
    
13. Failing that, Perl searches all parent packages listed in @classname::ISA, for any parent::AUTOLOAD subroutine. The search is again left-to-right, recursive, and depth-first.
    
14. 
    
15. Finally, Perl looks for a subroutine named UNIVERSAL::AUTOLOAD.
    
16. 
    
17. Perl stops after the first successful attempt and invokes that subroutine. If no subroutine is found, an exception is raised, one that you'll see frequently:
    
18. 
    

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