Date::Simple对象显示此行为,其中$date返回第二天的日期.
Date::Simple objects are immutable. After assigning $date1 to $date2,no change to $date1 can affect $date2. This means,for example,that there is nothing like a set_year operation,and $date++ assigns a new object to $date.
如何自定义对象的前/后增量行为,例如$object或$object–执行特定操作？
我已经浏览了perlboot,perltoot,perltooc和perlbot,但是我没有看到任何可以做到这一点的例子.
解决方法
你要
overload.
package Number;
use overload
'0+' => \&as_number,'++' => \&incr,;
sub new {
my ($class,$num) = @_;
return bless \$num => $class;
}
sub as_number {
my ($self) = @_;
return $$self;
}
sub incr {
my ($self) = @_;
$_[0] = Number->new($self->as_number + 1); # note the modification of $_[0]
return;
}
package main;
my $num = Number->new(5);
print $num . "\n"; # 5
print $num++ . "\n"; # 5
print ++$num . "\n"; # 7