C++ 错误：非静态成员引用必须相对于特定对象
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error:a nonstatic member reference must be relative to a specific object
提问by user1665569
I don't understand why view gives me the error of a nonstatic member reference must be relative to a specific object.
我不明白为什么视图给我非静态成员引用必须与特定对象相关的错误。
CDrawView::Shapeis an enum that i have declared on my CDrawView
CDrawView::Shape是我在我的 CDrawView
enum shape{line, rect, elli};
shape current_shape;
This is my other class
这是我的另一堂课
class Shapemaker
{
public:
CDrawView view;
static void Create(CDrawView::shape )
{
if(view.current_shape == view.line)
{
view.m_shape.reset(new Line());
}
else if(view.current_shape == view.rect)
{
view.m_shape.reset(new Rect());
}
}
}
What's the best practice to avoid this error
避免此错误的最佳做法是什么
回答by Joseph Mansfield
First of all, since the function is static, it doesn't have access to view. That's because viewis a non-static member of Shapemaker, so is only associated with specific instances o Shapemaker. Either viewneeds to be staticor the Createfunction shouldn't be. The other alternative is that viewshouldn't be a member and should be created inside the Createfunction.
首先，由于函数是static，它无权访问view. 那是因为view是 的非静态成员Shapemaker，所以仅与特定实例 o 相关联Shapemaker。无论是view需要被static或Create功能不应该。另一种选择是它view不应该是成员，而应该在Create函数内部创建。
Also, the enum constants' names are within the scope of the CDrawViewclass and are accessed through the class name like so:
此外，枚举常量的名称在CDrawView类的范围内，可以通过类名访问，如下所示：
if(view.current_shape == CDrawView::line)
The .operator is for accessing a non-static member of an object. viewdoes not have a non-static member called lineor rect.
该.运算符用于访问对象的非静态成员。view没有名为lineor的非静态成员rect。
回答by taocp
viewis a non-static object of class CDrawView, Createis static function of ShapeMakerclass, there will be no instance of viewif you do not construct an object of ShapeMakerwhile Createis not associated with any objects of ShapeMaker. You cannot use nons-tatic members inside a static member function.
view是类CDrawView的非静态对象，Create是类的 静态函数，如果不构造对象，则不ShapeMaker会有实例view，ShapeMaker而Create与ShapeMaker的任何对象都没有关联。您不能在静态成员函数中使用非静态成员。
