错误示范
// bar.h#ifndef BAR_H#define BAR_H#include "foo.h"class bar {public: foo getFoo();protected: foo f;};#endif//foo.h#ifndef FOO_H#define FOO_H#include "bar.h"class foo {public: bar getBar();protected: bar b;};#endif//main.cpp#include "foo.h"#include "bar.h"intmain (int argc, char **argv){ foo myFoo; bar myBar;}编译报错,foo/bar都包含不完整的类型
$ g++ main.cppIn file included from foo.h:3, from main.cpp:1:bar.h:6: error: ‘foo’ does not name a typebar.h:8: error: ‘foo’ does not name a type解决方案
- 用指针来指向需要包含的对象,使用前向声明来表示包含的那个类已存在
- 指针的大小是确定的,因此类的大小也就可以确定
- 避免了
A需要B需要A这种循环引用的问题
#ifndef BAR_H#define BAR_Hclass foo; // Say foo exists without defining it.class bar {public: foo* getFoo();protected: foo* f;};#endif #ifndef FOO_H#define FOO_Hclass bar; // Say bar exists without defining it.class foo {public: bar* getBar();protected: bar* f;};#endif 参考:
- https://stackoverflow.com/que...