是否有可能在C ++中创建可重新定义的命名空间别名？

Question

我想创建一个名称空间别名，可以全局更改以在运行时引用不同的作用域。考虑一下：

#include <iostream>

namespace scopePrimary {
    int somethingOfInterest = 1;
}
namespace scopeSecondary {
    int somethingOfInterest = 2;
}
namespace scopeTarget = scopePrimary;

int doStuffInTargetScope() {
    using namespace scopeTarget;
    return somethingOfInterest;
}

int main() {
    // Do something with the somethingOfInterest variable defined in scopePrimary
    std::cout << "doStuffInTargetScope():\n" \
    "  somethingOfInterest = " << doStuffInTargetScope() << std::endl;

    namespace scopeTarget = scopeSecondary;
    using namespace scopeTarget;

    // Do something with the somethingOfInterest variable defined in scopeSecondary
    std::cout << "doStuffInTargetScope():\n" \
    "  somethingOfInterest = " << doStuffInTargetScope() << std::endl;

    std::cout << "main():\n  somethingOfInterest = "
    << somethingOfInterest << std::endl;
}

现在，上面的代码确实编译了，但我不希望得到输出：

doStuffInTargetScope():
  somethingOfInterest = 1
doStuffInTargetScope():
  somethingOfInterest = 2
main():
  somethingOfInterest = 2

我得到这个输出：

doStuffInTargetScope():
  somethingOfInterest = 1
doStuffInTargetScope():
  somethingOfInterest = 1
main():
  somethingOfInterest = 2

似乎在尝试重新定义namespace scopeTarget时，C ++将只使用最本地的别名定义，而不是覆盖全局别名。有谁知道在这里实现我的目标的解决方案？

Answer 1

您无法在运行时更改名称空间。函数指针将达到预期的效果。

对于名称空间，请参阅：Renaming namespaces

对于函数指针，我发现这很有用：https://www.learncpp.com/cpp-tutorial/78-function-pointers/