perl bless 用法实例

程序包括5个文件：
person.pm ：实现了person类 
dog.pm ：实现了dog类 
bless.pl ： 正确的使用bless
bless.wrong.pl ： 错误的使用bless
bless.cc ： 使用C++语言实现了与bless.pl相同功能的代码


person.pm

#!/usr/bin/perl -w
package person;
use strict;
sub sleep() {
        my ($self) = @_;
        my $name = $self->{"name"};
        print("$name is person, he is sleeping\n");
}
sub study() {
        my ($self) = @_;
        my $name = $self->{"name"};
        print("$name is person, he is studying\n");
}
return 1;

dog.pm

#!/usr/bin/perl -w
package dog;
use strict;
sub sleep() {
        my ($self) = @_;
        my $name = $self->{"name"};
        print("$name is dog, he is sleeping\n");
}
sub bark() {
        my ($self) = @_;
        my $name = $self->{"name"};
        print("$name is dog, he is barking\n");
}
return 1;

bless.pl

#!/usr/bin/perl -w
use strict;
use person;
use dog;
sub main()
{
        my $object = {"name" => "tom"};
        # 先把"tom"变为人
        bless($object, "person");
        $object->sleep();
        $object->study();
        # 再把"tom"变为狗
        bless($object, "dog");
        $object->sleep();
        $object->bark();
        # 最后，再把"tom"变回人
        bless($object, "person");
        $object->sleep();
        $object->study();
}

使用c++实现bless的功能

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct object {
        char name[16];
};
struct person {
        char name[16];
        void sleep() { printf("%s is person, he is sleeping\n", this->name); }
        void study() { printf("%s is person, he is studying\n", this->name); }
};
struct dog {
        char name[16];
        void sleep() { printf("%s is dog, he is sleeping\n", this->name); }
        void bark() { printf("%s is dog, he is barking\n", this->name); }
};
#define bless(object, type) ((type*) object)
int main()
{
        struct object * o = (struct object *) malloc(sizeof(struct object));
        strcpy(o->name, "tom");
        // 先把"tom"变为人
        bless(o, person)->sleep();
        bless(o, person)->study();
        // 再把"tom"变为狗
        bless(o, dog)->sleep();
        bless(o, dog)->bark();
        // 最后，再把"tom"变回人
        bless(o, person)->sleep();
        bless(o, person)->study();
        return 0;
}

bless.wrong.pl

#!/usr/bin/perl =w
use strict;
use person;
use dog;

sub main()
{
        my $object = {"name" => "tom"};
        # 没有把类型信息和$object绑定，因此无法获知$object有sleep方法
        $object->sleep();
        $object->study();
}

程序运行输出为：

Can't call method "sleep" on unblessed reference at bless.wrong.pl line 10.