提升 ForEach 问题答案

【问题标题】：Boost ForEach Question提升 ForEach 问题
【发布时间】：2010-05-16 19:10:39
【问题描述】：

尝试使用类似下面的内容和 char 数组，但无法编译。但是带有 short[] 的示例可以正常工作。知道为什么吗？ :)

char someChars[] = {'s','h','e','r','r','y'};
    BOOST_FOREACH(char& currentChar, someChars)
    {

    }


short array_short[] = { 1, 2, 3 };
    BOOST_FOREACH( short & i, array_short )
    {
        ++i;
    }

【问题讨论】：

标签： c++ boost foreach

【解决方案1】：

如果您转到<boost/foreach.hpp> 中引发编译错误的行，您将看到以下注释：

// **** READ THIS IF YOUR COMPILE BREAKS HERE ****
//
// There is an ambiguity about how to iterate over arrays of char and wchar_t. 
// Should the last array element be treated as a null terminator to be skipped, or
// is it just like any other element in the array? To fix the problem, you must
// say which behavior you want.
//
// To treat the container as a null-terminated string, merely cast it to a
// char const *, as in BOOST_FOREACH( char ch, (char const *)"hello" ) ...
//
// To treat the container as an array, use boost::as_array() in <boost/range/as_array.hpp>,
// as in BOOST_FOREACH( char ch, boost::as_array("hello") ) ...

使用注释中显示的boost::as_array(someChars) 应该可以修复您的编译错误。

【讨论】：