C++ 模板 std::vector::iterator 错误 [英] C++ template std::vector::iterator error

问题描述

在 C++ 中，我试图为我的模板化类获取一个 std::vector::iterator.但是，当我编译它时，出现错误:error C2146: syntax error : missing ';'在标识符迭代器" 之前，错误 C4430:缺少类型说明符 - 假定为 int.注意:C++ 不支持 default-int.我也收到警告:warning C4346: 'std::vector::iterator' :dependent name is not a type:

In C++, I am trying to get a std::vector::iterator for my templated class. However, when I compile it, I get the errors: error C2146: syntax error : missing ';' before identifier 'iterator', error C4430: missing type specifier - int assumed. Note: C++ does not support default-int. I also get the warning: warning C4346: 'std::vector<T>::iterator' : dependent name is not a type:

#include <vector>
template<class T> class v1{
    typedef std::vector<T>::iterator iterator; // Error here
};
class v2{
    typedef std::vector<int>::iterator iterator; // (This works)
};

我什至尝试过

template<typename T> class v1{
    typedef std::vector<T>::iterator iterator;
};

和

template<typename T = int> class v1{
    typedef std::vector<T>::iterator iterator;
};

推荐答案

std::vector::iterator 是一个 依赖名称，所以这里需要一个typename来指定它指的是一个类型.否则，假定引用非类型:

std::vector<T>::iterator is a dependent name, so you need a typename here to specify that it refers to a type. Otherwise it is assumed to refer to a non-type:

typedef typename std::vector<T>::iterator iterator;

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