C ++本地类作为函子 [英] C++ local class as functor

问题描述

我试图使用本地类作为函子，并使用g ++（3.4.6）获取编译器错误。

I am trying to use a local class as a functor and get compiler error using g++ (3.4.6).

放置下面的类c> Processor ）解析错误，所以我猜测错误是因为函数局部结构/类。我更喜欢有在函数内的代码清晰和易于使用的类。

Placing the below class ( Processor ) in the global scope resolves the error, so I guess the error is because of function local structures/classes. I would prefer to have the classes inside the function for code clarity and ease of use. Want to know if there is a workaround solution to make the below code working.

test.cpp：24：error：没有匹配函数调用\ u2018foreachArg（& amp; char *& processSubs（int，char * ）:: Processor&）\\\’

test.cpp:24: error: no matching function for call to \u2018foreachArg(int&, char*&, processSubs(int, char*)::Processor&)\u2019

template <class Functor>
void foreachArg(int n, char *args[], Functor& f)
{
    for(int i=0; i<n; ++i)
        f(args[i]);
}

int processSubs(int argc, char *args[])
{
    class Processor
    {
        public:
            void operator()(const char *arg)
            {
            }
    };

    Processor p;
    foreachArg(argc, args, p);
}

int main(int argc, char *argv[])
{
    processSubs(argc, argv);
}

推荐答案

++ 11，用作模板函数的参数的类必须具有外部链接。本地类没有外部链接，所以你不能用这种方式。

In C++, prior to C++11, classes used as arguments to template functions must have external linkage. Local classes don't have external linkage so you can't use them this way.

C ++ 11改变了这一点，所以你可以通过设置你的编译器使用C ++ 11。

C++11 changes this, so you may be able to fix this by setting your compiler to use C++11.

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