perl中bless的理解
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
CODE:
#!/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;
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
CODE:
#!/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;
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
CODE:
#!/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();
}
&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
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();
}
&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
bless.wrong.pl
CODE:
#!/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();
}
&main();
# 程序运行输出为:
# Can't call method "sleep" on unblessed reference at bless.wrong.pl line 10.
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();
}
&main();
# 程序运行输出为:
# Can't call method "sleep" on unblessed reference at bless.wrong.pl line 10.
使用c++实现bless的功能
c中的代码
CODE:
#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;
}
// 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
#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;
}
// 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