A**u
发帖数: 2458 | 1 小弟在读effective c++, 第31节
讲到interface class, 里面提到 factory function, 有些不明白， 请大家指点
下面是代码.
interface class
class Person{
public:
static std::tr1::shared_ptr create(const std::string& name);
virtual ~Person();
virtual std::string name() const = 0;
}
这里的create 就是书里说的factory 函数
class RealPerson: public Person{
public:
RealPerson(const std::string& name):thename(name){}
virtual ~RealPerson();
std::string name() const;
private:
std::string the name;
}
奇怪的是 create 实现为
std::tr1::shared_ptr Person::create(const std::string& name)
{
return std::tr1::shared_ptr(new RealPerson(name));
}
关于create的实现，我有几点不明白
1.
create的实现是基类Person的， 它怎么能调用继承类的构造函数呢
2
create是static函数，static函数应该不可以访问非static数据和函数， 这里不是调
用了ctor?
谢谢指教 | t****t
发帖数: 6806 | 2
you can call RealPerson::RealPerson anywhere, because it is public.
same: you can call RealPerson::RealPerson anywhere, because it is public.
static member function can visit non-static members, as long as it provide
an object. you can visit non-static members anywhere, as long as you provide
an object (and it is public, if you visit it from non-member).
for ctor, you don't even need an object, because ctor create one.
【在 A**u 的大作中提到】
: 小弟在读effective c++, 第31节
: 讲到interface class, 里面提到 factory function, 有些不明白， 请大家指点
: 下面是代码.
: interface class
: class Person{
: public:
: static std::tr1::shared_ptr create(const std::string& name);
: virtual ~Person();
: virtual std::string name() const = 0;
: }
| A**u
发帖数: 2458 | 3 谢谢你的解答
一切都清除了
包子奉上
provide
【在 t****t 的大作中提到】
:
: you can call RealPerson::RealPerson anywhere, because it is public.
: same: you can call RealPerson::RealPerson anywhere, because it is public.
: static member function can visit non-static members, as long as it provide
: an object. you can visit non-static members anywhere, as long as you provide
: an object (and it is public, if you visit it from non-member).
: for ctor, you don't even need an object, because ctor create one.
| f******y
发帖数: 2971 | 4 Effective C++ is using tr1? Which version are you reading?
【在 A**u 的大作中提到】
: 小弟在读effective c++, 第31节
: 讲到interface class, 里面提到 factory function, 有些不明白， 请大家指点
: 下面是代码.
: interface class
: class Person{
: public:
: static std::tr1::shared_ptr create(const std::string& name);
: virtual ~Person();
: virtual std::string name() const = 0;
: }
| A**u
发帖数: 2458 | 5 3rd 最新的
【在 f******y 的大作中提到】
: Effective C++ is using tr1? Which version are you reading?
| r*******y
发帖数: 1081 | 6 I tried this but it is not working:
class A{
static A * f(){A * p= new B(); return p;}
};
class B: public A{
};
So what is the reason? Thanks.
provide
【在 t****t 的大作中提到】
:
: you can call RealPerson::RealPerson anywhere, because it is public.
: same: you can call RealPerson::RealPerson anywhere, because it is public.
: static member function can visit non-static members, as long as it provide
: an object. you can visit non-static members anywhere, as long as you provide
: an object (and it is public, if you visit it from non-member).
: for ctor, you don't even need an object, because ctor create one.
| t****t
发帖数: 6806 | 7 declare first, use later. so put A::f() after B.
【在 r*******y 的大作中提到】
: I tried this but it is not working:
: class A{
: static A * f(){A * p= new B(); return p;}
: };
: class B: public A{
: };
: So what is the reason? Thanks.
:
: provide
| r*******y
发帖数: 1081 | 8 Thanks a lot.
【在 t****t 的大作中提到】
: declare first, use later. so put A::f() after B.
|
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