I have this code in an Objective-C class (in an Objective-C++ file):
+(NSString *)readString
{
string res;
std::getline(cin, res);
return [NSString stringWithCString:res.c_str() encoding:NSASCIIStringEncoding];
}
When I run it, I get a zero-length string, Every time. Never given the chance to type at the command line. Nothing. When I copy this code verbatim into main()
, it works. I have ARC on under Build Settings. I have no clue what it going on. OSX 10.7.4, Xcode 4.3.2.
It is a console application.
It means there is input waiting to be read on the input. You can empty the input:
cin.ignore(std::numeric_limits<std::streamsize>::max();
std::getline(cin, res);
If this is happening it means you did not read all the data off the input stream in a previous read. The above code will trash any user input before trying to read more.
This probably means that you are mixing operator>>
with std::getline()
for reading user input. You should probably pick one technique and use that (std::getline()) throughout your application ( you can mix them you just have to be more careful and remove the '\\n' after using operator>> to make sure any subsequent std::getline() is not confused..
If you want to read a number read the line then parse the number out of the line:
std::getline(cin, line);
std::stringstream linestream(line);
linestream >> value;
You can simply do:
cin.ignore();
or use
cin.clear();
cin.sync();
before using getline()
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