12.5.2 访问被覆盖的方法

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12.5.2  访问被覆盖的方法当一个类定义一个方法,那么该子过程覆盖任意基类中同名的方法。想象一下你有一个Mule(骡)对象(它是从Horse(马)类和Donkey（驴）类衍生而来的)$stallion = Horse->new(gender => "male"); 男性$molly = Mule->new(gender => "female"); 女性$colt = $molly->breed($stallion);这就是SUPER 伪类提供便利的地方,它令你能够调用一个覆盖了的基类方法,而不用声明哪个类定义了该方法。[root@node01 aaa]# cat Horse.pm package Horse;    our @ISA = "Critter";    require Critter;    sub new {    my $invocant = shift;    my $class = ref($invocant) || $invocant;    my $self = {    color => "bay",    legs => 4,    owner => undef,    @_, # 覆盖以前的属性    };    return bless $self, $class;    #return  $self;    };    sub sum1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b + 7;    };     sub kick {    my $self=shift;    $self->SUPER::kick(@_);  };  1; Horse 类继承了Critter 类[root@node01 aaa]# cat Critter.pm package Critter;    sub new {        my $self = {};        my $invocant = shift;        my $class = ref($invocant) || $invocant;        my ($name)=@_;              my $self = {                 "name" =>$name                         };          bless $self, $class; # Use class name to bless() reference        return $self;        };        sub sum2 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b;    };            sub fun1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a / $b;    }      sub kick {        my  $self=shift;         my $a=shift;         my $b=shift;         return $a / $b +66;  }    1;  [root@node01 aaa]# cat a1.pl use Horse;  use Data::Dumper;    $steed = Horse->new(color => "dun");  print $steed->kick(12,4);  print "\n";  [root@node01 aaa]# perl a1.pl 69此时调用了Critter.pm  类的kick  方法:[root@node01 aaa]# cat Critter.pm package Critter;    our @ISA = "Mule";    require Mule;  sub new {        my $self = {};        my $invocant = shift;        my $class = ref($invocant) || $invocant;        my ($name)=@_;              my $self = {                 "name" =>$name                         };          bless $self, $class; # Use class name to bless() reference        return $self;        };        sub sum2 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b;    };            sub fun1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a / $b;    }      sub kick {        my  $self=shift;         my $a=shift;         my $b=shift;         return $a / $b +66;  }    1;   让 Critter 继承Mule 类[root@node01 aaa]# cat Mule.pm package Mule;sub kick {        my  $self=shift;         my $a=shift;         my $b=shift;         return $a * $b +66;  }    1;[root@node01 aaa]# perl a1.pl 69修改[root@node01 aaa]# cat Critter.pm package Critter;    our @ISA = "Mule";    require Mule;  sub new {        my $self = {};        my $invocant = shift;        my $class = ref($invocant) || $invocant;        my ($name)=@_;              my $self = {                 "name" =>$name                         };          bless $self, $class; # Use class name to bless() reference        return $self;        };        sub sum2 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b;    };            sub fun1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a / $b;    }       sub kick {    my $self=shift;    $self->SUPER::kick(@_);  };  1;[root@node01 aaa]# cat a1.pl use Horse;  use Data::Dumper;    $steed = Horse->new(color => "dun");  print $steed->kick(12,4);  print "\n";  [root@node01 aaa]# perl a1.pl 114当一个类定义一个方法，那么该子过程覆盖任意基类中同名的方法:[root@node01 111]# cat Horse.pm package Horse;    our @ISA = "Critter";    require Critter;    sub new {    my $invocant = shift;    my $class = ref($invocant) || $invocant;    my $self = {    color => "bay",    legs => 4,    owner => undef,    @_, # 覆盖以前的属性    };    return bless $self, $class;    #return  $self;    };    sub sum1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b + 7;    };     sub kick {    my $self=shift;    my $a=shift;  my $b=shift;  return $a * $b;};  1;  [root@node01 111]# cat Critter.pm package Critter;    our @ISA = "Mule";    require Mule;  sub new {        my $self = {};        my $invocant = shift;        my $class = ref($invocant) || $invocant;        my ($name)=@_;              my $self = {                 "name" =>$name                         };          bless $self, $class; # Use class name to bless() reference        return $self;        };        sub sum2 {           $self=shift;           my $a=shift;           my $b=shift;           return $a + $b;    };            sub fun1 {           $self=shift;           my $a=shift;           my $b=shift;           return $a / $b;    }       sub kick {    my $self=shift;    my $a=shift;  my $b=shift;  return $a/$b +5;};  1;    [root@node01 111]# cat a1.pl use Horse;  use Data::Dumper;    $steed = Horse->new(color => "dun");  print $steed->kick(12,4);  print "\n";  [root@node01 111]# perl a1.pl 48此时没有去访问基类的方法:Mule （骡）类的设计者通过给 Mule（骡）类写自己的 breed 方法覆盖了那些父类的 breed 方法。这这意味着下面的交叉引用可能不能正确工作：$stallion = Horse->new(gender => "male"); 男性$molly = Mule->new(gender => "female");    女性$colt = $molly->breed($stallion);
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