如何在Perl中有条件地使用模块？

I want to do something like this in Perl:

我想在Perl中做这样的事情：

$Module1="ReportHashFile1"; # ReportHashFile1.pm
$Module2="ReportHashFile2"; # ReportHashFile2.pm

if(Condition1)
{
  use $Module1;
}
elsif(Condition2)
{
  use $Module2;
}

ReportHashFile*.pm contains a package ReportHashFile* .

ReportHashFile * .pm包含一个包ReportHashFile *。

Also how to reference an array inside module based on dynamic module name?

如何根据动态模块名称引用模块内部的数组？

@Array= @$Module1::Array_inside_module;

Is there anyway I can achieve this. Some sort of compiler directive?

无论如何我能做到这一点。某种编译器指令？

3 个解决方案

#1

You might find the if module useful for this.

您可能会发现if模块对此有用。

Otherwise the basic idea is to use require, which happens at run-time, instead of use, which happens at compile-time. Note that '

否则，基本思想是使用require，它在运行时发生，而不是在编译时发生。注意 '

BEGIN {
    my $module = $condition ? $Module1 : $Module2;
    my $file = $module;
    $file =~ s[::][/]g;
    $file .= '.pm';
    require $file;
    $module->import;
}

As for addressing globals, it might be easier if you just exported the variable or a function returning it to the caller, which you could use by its unqualified name. Otherwise there's also the possibility of using a method and calling it as $Module->method_name.

至于寻址全局变量，如果您只是导出变量或将函数返回给调用者，可能会更容易，您可以通过其非限定名称使用它。否则，也可以使用方法并将其作为$ Module-> method_name调用。

Alternatively, you could use symbolic references as documented in perlref. However, that's usually quite a code smell.

或者，您可以使用perlref中记录的符号引用。然而，这通常是代码味道。

my @array = do {
    no strict 'refs';
    @{ ${ "${Module}::Array_inside_module" } };
};

#2

Unless the execution speed is important, you can use string eval:

除非执行速度很重要，否则可以使用字符串eval：

if (Condition1) {
    eval "use $Module1"; die $@ if $@;
}
elsif (Condition2) {
    eval "use $Module2"; die $@ if $@;
}

#3

People have already told you how you can load the module with Perl primitives. There's also Module::Load::Conditional.

人们已经告诉过你如何使用Perl原语加载模块。还有Module :: Load :: Conditional。

If you're looking to access an array of the same name no matter which module you loaded, consider making a method for that so you can skip the symbolic reference stuff. Give each module a method of the same name:

如果你想要访问一个同名的数组，无论你加载哪个模块，考虑为它制作一个方法，这样你就可以跳过符号引用的东西。为每个模块提供一个相同名称的方法：

  package ReportHashFileFoo;
  our @some_package_variable;
  sub get_array { \@some_package_variable }

Then, when you load that module:

然后，当您加载该模块时：

  if( ... some condition ... ) {
       eval "use $module" or croak ...;
       my $array_ref = $module->get_array;
       }

I don't know what you're really doing (XY Problem), but there's probably a better design. When things seem tricky like this, it's usually because you're overlooking a better way to to it.

我不知道你在做什么（XY问题），但可能有更好的设计。当事情看起来像这样棘手时，通常是因为你忽视了一种更好的方法。

#1