如何将 BOOST_FOREACH 与 boost::ptr_map 一起使用?

2021-12-24 00:00:00 c++ boost

如何通过 boost::ptr_map 有效地使用 BOOST_FOREACH(字符数/可读性)?

How can I use BOOST_FOREACH efficiently (number-of-character/readability-wise) with a boost::ptr_map?

Kristo 在他的回答中证明这是可能的将 BOOST_FOREACH 与 ptr_map 一起使用，但与使用迭代器迭代 ptr_map 相比，它并没有真正为我节省任何输入(或使我的代码真正更具可读性):

Kristo demonstrated in his answer that it is possible to use BOOST_FOREACH with a ptr_map, but it does not really save me any typing (or makes my code really more readable) than iterating over the ptr_map with an iterator:

typedef boost::ptr_container_detail::ref_pair<int, int* const> IntPair;
BOOST_FOREACH(IntPair p, mymap) {
    int i = p.first;
}

// vs.

boost::ptr_map<int, T>::iterator it;
for (it = mymap.begin(); it != mymap.end(); ++it) {
    // doSomething()
}

以下代码符合我的愿望.它遵循有关如何将 BOOST_FOREACH 与 std::map 一起使用的标准方法.不幸的是，这不能编译:

The following code is somewhere along the lines what I wish for. It follows the standard way on how to use BOOST_FOREACH with a std::map. Unfortunately this does not compile:

boost::ptr_map<int, T> mymap;
// insert something into mymap
// ...

typedef pair<int, T> IntTpair;
BOOST_FOREACH (IntTpair &p, mymap) {
    int i = p.first;
}

推荐答案

作为 STL 风格的容器，指针容器有一个 value_type 类型定义，你可以使用:

As STL style containers, the pointer containers have a value_type typedef that you can use:

#include <boost/ptr_container/ptr_map.hpp>
#include <boost/foreach.hpp>

int main()
{
    typedef boost::ptr_map<int, int> int_map;
    int_map mymap;

    BOOST_FOREACH(int_map::value_type p, mymap)
    {
    }
}

我发现为容器使用 typedef 会使代码更容易编写.

I find that using a typedef for the container makes the code a lot easier to write.

另外，你应该尽量避免在 boost 中使用 detail 命名空间的内容，这是一个包含实现细节的 boost 约定.

Also, you should try to avoid using the contents of detail namespaces in boost, it's a boost convention that they contain implementation details.

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