Question

I have a method that that creates a MatLab array name from a file path and returns it as a std::string. the resulting string is passed into another method that writes the name to the file. When I try to get the length of the passed in string, it displays 0 when the length of the string is 12 or 13 chars.

My code:

bool MyClass::masterMethod(std::string fileURI){

 FILE* dataStream;
 // Assume dataStream is set up correctly

 // Get arrayName from File URI
 std::string arrayName = this->makeArrayNameFromPath( fileURI);

 //Write array name to file
 this->writeArrayName(arrayName , dataStream)



}


std::string MyClass::makeArrayNameFromPath(std::string filePathURI){


std::string tempString = filePathURI.substr(filePathURI.find_last_of('/')+1); 

std::string returnString = "";

long index = 0;

for(long i = 0; i < tempString.length(); i++){

    if((tempString[i] != ' ') && (tempString[i] != '.')){

        returnString[index++] = tempString[i];
    }
}

return returnString;

}



void MyClass::writeArrayName(std::string name , FILE *nameStream){

 // long testLength = name.length();
 // long testLength2 = name.size();
 // const char* testChar = nam.c_str();
 // long testCharLen = strlen(testChar);    

// The size of the name is the number of Chars * sizeof(int8_t)
int32_t sizeOfName = (int32_t)(name.length() * sizeof(int8_t));
int32_t nameType = miINT8;

fwrite(&nameType , sizeof(int32_t) , 1 , nameStream);
fwrite(&sizeOfName, sizeof(sizeOfName), 1, nameStream);
fwrite(&name , sizeof(name[0]), sizeOfName , nameStream);   

}

So I’m not sure why string::length is not working. If a create a std::string test = name, and print it , I can get the value of the string but can not get its length or size.
If I use const char* testName = name.c_str(); long test = strlen(testName), I get a the
correct value, but thought that wasn’t necessary.

So any advice or suggestion is appreciated.

Answer 1

returnString[index++] = tempString[i]; doesn’t do what you think it does. It’s not adding additional space or length to the string, only overwriting memory at a location that the string doesn’t actually own. I think returnString.append(1, tempString[i]) or similar should do it.