如何声明和实现const和内联成员函数？

Question

码:

point3f.h

Class Point3f {
     ...
     inline void project2D(ProjType p, const Point2i& view) const;
};

point3f.cpp

inline void Point3f::project2D(ProjType p, const Point2i& view) const {
    switch(p) {
        case PROJ_XY:
            glVertex2f(x * view.x, y * view.y);
            break;
        case PROJ_YZ:
            glVertex2f(y * view.x, z * view.y);
            break;
        case PROJ_XZ:
            glVertex2f(x * view.x, z * view.y);
            break;
        default:
            break;
    }
}

调用此函数会在编译时引发错误:

    undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'

我试过没有和用inline符号的每个案例:

inline 在标题中,而不是在cpp中:

 Warning: inline function ‘void Point3f::project2D(ProjType, const Point2i&) const’ used but never defined [enabled by default
 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline 在标题中,也在cpp中:

 Warning: inline function ‘void Point3f::project2D(ProjType, const Point2i&) const’ used but never defined [enabled by default
 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline 不是在标题中,而是在cpp中:

 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline 不在标题中,也不在cpp中:

 It works but that's not what I want

题:

1. 是否const and inline member function有意义？
2. 如何申报const and inline member function？

提前致谢.

Answer 1

功能const与它无关.如果需要inline,则必须在头文件中而不是在头文件中定义它point3f.cpp.例:

class Point3f {
    ...
    inline void project2D(ProjType p, const Point2i& view) const
    {
        switch(p) {
        case PROJ_XY:
            glVertex2f(x * view.x, y * view.y);
            break;
        case PROJ_YZ:
            glVertex2f(y * view.x, z * view.y);
            break;
        case PROJ_XZ:
            glVertex2f(x * view.x, z * view.y);
            break;
        default:
            break;
        }
    }
};

在这种情况下,inline根本不需要关键字.如果在类定义中定义函数,inline则为默认值.但是如果你愿意,你仍然可以指定它(正如我在上面的例子中所做的那样).