perl - 如何在 Perl 中创建嵌套哈希作为常量？

Question

我想在 Perl 中执行以下 Ruby 代码的等效操作:

class Foo
  MY_CONST = {
    'foo' => 'bar',
    'baz' => {
      'innerbar' => 'bleh'
    },
  }

  def some_method
    a = MY_CONST[ 'foo' ]
  end

end

# In some other file which uses Foo...

b = Foo::MY_CONST[ 'baz' ][ 'innerbar' ]

也就是说，我只想声明一个常量、嵌套的哈希结构，以便在类中和外部使用。如何？

Answer 1

您也可以完全使用内置函数执行此操作:

package Foo;
use constant MY_CONST =>
{
    'foo' => 'bar',
    'baz' => {
        'innerbar' => 'bleh',
    },
};

sub some_method
{
    # presumably $a is defined somewhere else...
    # or perhaps you mean to dereference a parameter passed in?
    # in that case, use ${$_[0]} = MY_CONST->{foo} and call some_method(\$var);
    $a = MY_CONST->{foo};
}

package Main;  # or any other namespace that isn't Foo...
# ...
my $b = Foo->MY_CONST->{baz}{innerbar};