将字符移动到字符串中会使迭代器无效吗? [英] Does moving characters into string invalidate iterators?

问题描述

因此遍历字符串并使用operator[]或插入以更改字符可以使迭代器无效.

So iterating over a string and using operator[] or insert to change characters can invalidate the iterator.

像这样的迭代也是这样吗?

Is that also the case for an iteration like this?

std::string str = "ABCD";
for(auto&& c : str){
    for(int i = 0; i < 3; ++i){
        switch(c) {
            case 'A':
                c = 'B';
                break;
            case 'B':
                c = 'C';
                break;
            /*...*/
        }
        //do something
    }
}

此代码适用于gcc和msvc，但我不知道我是否可以信任它.我正在使用C ++ 14.

This code works on gcc and msvc but I don't know if I can trust it. I'm using C++14.

推荐答案

您正在修改字符串的现有字符，因此它是完全安全的.当字符串存储区的大小可能更改时，例如，迭代器无效.当您添加新字符时，可能需要分配更大的字符串缓冲区，因此所有指向先前缓冲区的迭代器都可能无效.

You are modifying existing characters of string so it is completely safe. Iterators are invalidated when the size of the string storage may change, e.g. when you append a new character, there might be a need to allocate a bigger string buffer, so all the iterators pointing to previous buffer may become invalid.

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