我对 Perl 构造函数中发生的事情有点困惑。我找到了这两个例子 perldoc perlbot .
package Foo;
#In Perl, the constructor is just a subroutine called new.
sub new {
#I don't get what this line does at all, but I always see it. Do I need it?
my $type = shift;
#I'm turning the array of inputs into a hash, called parameters.
my %params = @_;
#I'm making a new hash called $self to store my instance variables?
my $self = {};
#I'm adding two values to the instance variables called "High" and "Low".
#But I'm not sure how $params{'High'} has any meaning, since it was an
#array, and I turned it into a hash.
$self->{'High'} = $params{'High'};
$self->{'Low'} = $params{'Low'};
#Even though I read the page on [bless][2], I still don't get what it does.
bless $self, $type;
}
另一个例子是:
package Bar;
sub new {
my $type = shift;
#I still don't see how I can just turn an array into a hash and expect things
#to work out for me.
my %params = @_;
my $self = [];
#Exactly where did params{'Left'} and params{'Right'} come from?
$self->[0] = $params{'Left'};
$self->[1] = $params{'Right'};
#and again with the bless.
bless $self, $type;
}
这是使用这些对象的脚本:
package main;
$a = Foo->new( 'High' => 42, 'Low' => 11 );
print "High=$a->{'High'}\n";
print "Low=$a->{'Low'}\n";
$b = Bar->new( 'Left' => 78, 'Right' => 40 );
print "Left=$b->[0]\n";
print "Right=$b->[1]\n";
我已经将我一直在代码中的问题/困惑作为注释注入(inject)了。
最佳答案
您的问题与 OO Perl 无关。您对数据结构感到困惑。
可以使用列表或数组初始化哈希:
my @x = ('High' => 42, 'Low' => 11);
my %h = @x;
use Data::Dumper;
print Dumper \%h;
$VAR1 = { 'Low' => 11, 'High' => 42 };
When you invoke a method on a bless
ed reference, the reference is prepended to the argument list the method receives:
#!/usr/bin/perl
package My::Mod;
use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Indent = 0;
sub new { bless [] => shift }
sub frobnicate { Dumper(\@_) }
package main;
use strict;
use warnings;
my $x = My::Mod->new;
# invoke instance method
print $x->frobnicate('High' => 42, 'Low' => 11);
# invoke class method
print My::Mod->frobnicate('High' => 42, 'Low' => 11);
# call sub frobnicate in package My::Mod
print My::Mod::frobnicate('High' => 42, 'Low' => 11);
输出:
$VAR1 = [bless([], 'My::Mod'),'High',42,'Low',11];
$VAR1 = ['My::Mod','High',42,'Low',11];
$VAR1 = ['高',42,'低',11];
关于perl - 面向对象的 Perl 构造函数语法和命名参数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1703046/