使用局部对象指针的简单样式问题及其功能 [英] Simple style question using local object pointer and its function

问题描述

这种样式可以吗?

Is this style OK?

#include "BaseClass.h"

CMyClass::AFunction( CData & goodData )
{

CBaseClass * baseClass;               // don''t really need an instance      
baseClass->AgentFunction( goodData ); // just the use of its function

}

我喜欢简单.我注意到我无法通过嵌入CBaseClass或使用CBaseClass ::
来做到这一点
另外，我注意到我不必初始化为NULL，并且想知道我应该说= 0还是= NULL.

I like the simplicity. I noticed I couldn''t do it by embedding CBaseClass or using CBaseClass::

Also, I noticed I didn''t have to initialize to NULL, and wondered should I say = 0, or = NULL.

推荐答案

Brian Bennett写道:

Brian Bennett wrote:

CBaseClass * baseClass; //并不需要实例
baseClass-> AgentFunction(goodData); //仅使用其功能

CBaseClass * baseClass; // don''t really need an instance
baseClass->AgentFunction( goodData ); // just the use of its function

如果您喜欢简单性，为什么不使用AgentFunction方法static?

:)

If you like simplicity why then didn''t you make AgentFunction method static?

:)

您必须确保以这种方式调用的函数不使用该类的任何成员变量(全部通过其调用链).

You must make sure that a function invoked this way doesn''t make use of any member variables of that class (all through its call chain).

Cpallini的答案涵盖了静态成员函数的模拟.

如果您使用的是C ++ 98编译器，请使用0而不是NULL. 0与C ++中的任何指针类型都兼容，并且如果操作系统需要其他功能，则取决于编译器进行转换. NULL仅是C程序员的舒适毯子，并且(在我使用过的每个C ++编译器中，NULL都被定义为0).

如果您使用的是C ++ 0x，则可以使用nullptr.这是类型为nullptr_t的变量，该变量再次与任何其他指针类型兼容.

干杯，

灰

PS:针对以下评论...

NULL的问题在于，它为C ++中的空"指针值提供了0的尴尬感.过去C的人们认为NULL是(void *)0，但是在C ++中，这是完全垃圾.然后，当他们尝试实例化模板或使用模板调用重载函数时，他们会感到非常困惑，并且发生了一些完全棘手的事情.另一方面，如果您使用普通的旧0，那么您将毫无疑问地认为它是模棱两可的，并且在创建或调用int专业化或覆盖时，也不会因此而感到惊讶.

Cpallini''s answer covers the simulation of a static member function.

If you''re using a C++98 compiler then use 0 rather than NULL. 0 is type compatible with any pointer type in C++ and if the OS wants something else it''s up to the compiler to do the conversion. NULL is only there as a comfort blanket to C programmers and is (on every C++ compiler I''ve used, 10 of them) defined as 0.

If you''re using C++0x then you can use nullptr. This is a variable of type nullptr_t which, again, is type compatible with any other pointer type.

Cheers,

Ash

PS: In response to the comment below...

The problem with NULL is that it gives a fig leaf over the embarrassment of 0 for the "null" pointer value in C++. People used to C think that NULL is (void *)0, however in C++ this is complete rubbish. They then get very confused when they try and instantiate a template or call an overloaded function with it and something completely screwy happens. On the other hand if you use plain old 0 then you''ll be under no illusions that it''s ambiguous and won''t be (so) surpised when the int specialisation or override gets created or called.

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