如何获取对父 class 子例程 perl 的引用

Question

我有一种情况，在子 class 中，我需要父 class 中定义的子例程的引用，我需要将其传递给其他 class 来执行它们。所以我写了下面的示例模块来测试它们。

Parent1.pm

package Parent1;

sub new {
    my ($class, $arg_hash) = @_;

    my $self = bless $arg_hash, $class; 

    return $self;
}

sub printHello{

    print "Hello\n";
}

sub printNasty{
    print "Nasty\n";
}
1;

Child1.pm

package Child1; 

use base Parent1;

sub new {
    my ($class, $arg_hash) = @_;

    my $self = bless $arg_hash, $class; 

    return $self;
}

sub testFunctionReferences{

    my ($self) = @_;

    # Case 1: Below 2 lines of code doesn't work and produces error message "Not a CODE reference at Child1.pm line 18."
    #my $parent_hello_reference = \&$self->SUPER::printHello;
    #&$parent_hello_reference();

    # Case 2: Out of below 2 lines of code, 1st line executes the function and produces output of "Hello\n" but 2nd line doesn't work and produces error message "Not a CODE reference at Child1.pm line 23."
    #my $parent_hello_reference2 = $self->SUPER::printHello;
    #&$parent_hello_reference2();

    # Case 3: does not work either. Says "Undefined subroutine &Child1::printNasty called at Child1.pm line 27"
    #my $parent_nasty_reference = \&printNasty;
    #&$parent_nasty_reference();

    # Case 4: works. prints "World\n" as expected  
    #my $my_own_function_reference = \&printWorld;
    #&$my_own_function_reference();

    # Case 5: works. prints "Hello\n" and  "Nasty\n" as expected
    #$self->printHello();
    #$self->SUPER::printNasty();

    # Case 6: does not work produces error "Undefined subroutine &Child1::printHello called at Child1.pm line 38" 
    #printHello();
    return;
}

sub printWorld{
    print "World\n";
}

test.pl

#!/usr/bin/perl

use Child1;

my $child = Child1->new({});

$child->testFunctionReferences();

所以我的问题是：

与情况 1 一样，获取对父子例程的引用的正确语法是什么？
使用继承时，如何像案例6那样直接调用父函数？在perl中甚至可能吗？
当情况 5 有效时，为什么情况 6 不行？

如有任何见解，我们将不胜感激。谢谢

Answer 1

如果printHello是一个子程序，使用

my $sub = \&Parent::printHello;

如果printHello是一个方法，使用

# This line must appear inside of the Child package.
my $sub = sub { $self->SUPER::method(@_) };

如果你想要代码引用，你需要一个子程序来引用，这就创建了一个。

在这两种情况下，您都可以使用

调用子程序

&$sub();

或

$sub->();

（我觉得后者更干净，但它们在其他方面是等价的。）

Answer 2

我想出了另一种方法来使用 'UNIVERSAL' 模块 'can' 方法获取对父 class 子例程的引用。

#Parent.pm

        package Parent;

        sub new {
            my ($class, $arg_hash) = @_;
            my $self = bless $arg_hash, $class; 
            return $self;
        }

        sub printHello{
            print "Parent Hello Called\n";
        }

        1;


#Child.pm
        package Child;
        use base Parent;

        sub new {
            my ($class, $arg_hash) = @_;
            my $self = bless $arg_hash, $class; 
            return $self;
        }

        sub getParentSubReference{
            my ($self) = @_;
            return $self->can('printHello');
        }  

        1;


#test.pl

        #!/usr/bin/perl
        use Child;

        my $obj = Child->new({});
        my $ref = $obj->getParentSubReference();
        &$ref();


#Output
        Parent Hello Called

如何获取对父 class 子例程 perl 的引用

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Parent1.pm

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