学步园

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;

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;

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();
}

&main();

# 程序运行时输出：
# tom is person, he is sleeping
# tom is person, he is studying
# tom is dog, he is sleeping
# tom is dog, he is barking
# tom is person, he is sleeping
# tom is person, he is studying

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();
}

&main();

# 程序运行输出为：
# Can't call method "sleep" on unblessed reference at bless.wrong.pl line 10.

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;
}

// 程序运行时输出：
// tom is person, he is sleeping
// tom is person, he is studying
// tom is dog, he is sleeping
// tom is dog, he is barking
// tom is person, he is sleeping
// tom is person, he is studying