C++迭代器或包装器适配器示例 _C++

如果你想把一个可迭代范围和另一个在某种程度上转换底层迭代器，并允许循环或构造其他对象:

for (auto ch : Upper("abcdef")) { // Prints "ABCDEF" std::cout < < ch; } Upper up(std::string("fOo")); std::string newfoo(std::begin(up), std::end(up)); assert(newfoo == "FOO");

然后，类似于一个普通的迭代范围，你将需要创建一个范围类和一个迭代器类:

class myit { private: std::string::const_iterator wrapped_; class charholder { const char value_; public: charholder(const char value) : value_(value) {} char operator*() const { return value_; } }; public: // Previously provided by std::iterator typedef intvalue_type; typedef std::ptrdiff_tdifference_type; typedef int*pointer; typedef int& reference; typedef std::input_iterator_tag iterator_category; explicit myit(std::string::const_iterator wrapped) : wrapped_(wrapped) {} value_type operator*() const { return std::toupper(*wrapped_); } bool operator==(const myit& other) const { return wrapped_ == other.wrapped_; } bool operator!=(const myit& other) const { return !(*this == other); } charholder operator++(int) { charholder ret(std::toupper(*wrapped_)); ++wrapped_; return ret; } myit& operator++() { ++wrapped_; return *this; } }; class Upper { private: const std::string str_; public: Upper(const std::string str) : str_(str) {} myit begin() { return myit(std::begin(str_)); } myit end(){ return myit(std::end(str_)); } };

【C++迭代器或包装器适配器示例】请注意需要调用转换/适应函数std::toupper在两个地方。更新:std::iterator在c++ 17中是不推荐的，因此被删除。