如何检查视频或音频文件格式是否可以在iphone中以编程方式播放？(How to check whether a video or audio file format is playable in iPhone programmatically?)

 创建字符串的副本并对其进行修改，然后将其设置回来（如果这是您需要的）。 
 
std::string newid = some_reader->Key();
int start_index = newid.find("something");
newid.erase(start_index, 3);

some_reader->SetKey(newid); // if required and possible
 
 除非你知道你在做什么，为什么要这样做并考虑了所有其他选择，否则应该避免其他路线......在这种情况下，你首先不需要问这个问题。 

Create a copy of the string and modify that, then set it back (if that's what you need).
 
std::string newid = some_reader->Key();
int start_index = newid.find("something");
newid.erase(start_index, 3);

some_reader->SetKey(newid); // if required and possible
 
Other routes shall be avoided unless you know what you're doing, why you're doing it and have considered all other options ... in which case you would never need to ask this question in the first place.