Conversion from string to char - c++

For a program I'm writing based on specifications, a variable is passed in to a function as a string. I need to set that string to a char variable in order to set another variable. How would I go about doing this?

This is it in the header file:

void setDisplayChar(char displayCharToSet);

this is the function that sets it:

void Entity::setElementData(string elementName, string value){
    if(elementName == "name"){
            setName(value);
    }
    else if(elementName == "displayChar"){
    //      char c;
      //      c = value.c_str();
            setDisplayChar('x');//cant get it to convert :(
    }
    else if(elementName == "property"){
            this->properties.push_back(value);
    }
}

Thanks for the help in advanced!