C++ 类型的值不能分配给类型的实体
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a value of type cannot be assigned to an entity of type
提问by Dionysis Nt.
I have a header file in c++ with a namespace and a class in it
我在 C++ 中有一个头文件，其中有一个命名空间和一个类
namespace imaging{
class Image
{
// to index individual channels
protected:
Component * buffer; // Holds the image data
Image(unsigned int width, unsigned int height, const Component * data_ptr, bool interleaved=false);
}
}
when i try to implement the constructor i get an error a value of type cannot be assigned to an entity of type.
当我尝试实现构造函数时，我收到一个错误类型的值无法分配给类型的实体。
#include Image.h
namespace imaging
{
Image::Image(unsigned int width, unsigned int height, const Component * data_ptr, bool interleaved=false)
{
this->height=height;
this->width=width;
buffer=data_ptr; // The error is here!!
}
}
回答by Amxx
data_ptris as const Component *while Image::bufferis a Component *
data_ptr是作为const Component *同时Image::buffer是一个Component *
By affecting the first to the second you would discard the const. The whole point of this attribute is to protect data and it should be removed by a simple cast.
通过影响第一个到第二个，您将丢弃const. 此属性的全部意义在于保护数据，应该通过简单的强制转换将其删除。
You could either edite you constructor argument's type to remove the constor use
您可以编辑构造函数参数的类型以删除const或使用
buffer=const_cast<Component*>(data_ptr);
In any case, think about the behaviour you want. Is there any sens for the pointer to be const (it's not a ref) ?
无论如何，请考虑您想要的行为。指针是否有任何意义为 const （它不是参考）？
