Elysian Shadows

Posted: **Thu Sep 23, 2010 5:20 pm**

Hey guys, I was writing some code and I found a peculiar error. The function convert_vector2d(&i_scale) converts a string to a vector2d (inherits from sf::vector2f). If you examine the next few lines of code, I am doing the same operation twice.

Code: Select all

float x = convert_Vector2D(&i_scale).x;
float y = convert_Vector2D(&i_scale).y;
object.SetScale( ( convert_Vector2D(&i_scale) ) );
ss = object.GetScale();
object.SetScale( x , y );
ss = object.GetScale();

First time I call setScale with the return vector from convert_vector2d and ss = 1,1. I then call object.setScale again this time with x, y (the stored results) and when I call object.getScale I get ss = 1,2 (which is expected/correct).

I stepped through the convert function and it returns 1,2 through both function calls.

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const Vector2D Map::convert_Vector2D(std::string * string_to_convert)
{
    size_t foundit = 0;
    Vector2D temp;
    std::string one, two;
    if( (foundit = string_to_convert->find(',')) != std::string::npos &&
        string_to_convert->find_first_of(',') == string_to_convert->find_last_of(',') ) // only one comma per line.
    {
        one = string_to_convert->substr(0, foundit);
        two = string_to_convert->substr(foundit+1, string_to_convert->size()); // +1 to skip over the comma.

        temp.x = (float)strtod( one.c_str(), NULL );
        temp.y = (float)strtod( two.c_str(), NULL );

        check_conversion_errors_vector2d(temp, string_to_convert);
    }
    else
    {
        Debugger::print("MapLoader: Error: more then one comma on line %d of file %s. Stopping reading of file.\n", 
            i_Current_Line, mMapName.c_str() );
        i_QuitParsing = true; // TODO: maybe add return after this line?
    }

    return temp;
}

Any ideas on why I'm getting different behavior?

edit: I'm also having a conversation about it on stackoverflow: http://stackoverflow.com/questions/3782 ... directly-c

Posted: **Fri Sep 24, 2010 1:02 am**

Okay, so by having Vector2D inherit from vector2f and defining member variables x,y in both caused an error. I removed the declaration of x,y in vector2d (inherited class) and it works perfectly. I guess the compiler wasn't sure which x,y was supposed to be updated. Does anyone know EXACTLY what happens if you declare x,y in a base class and an inherited class?

Posted: **Fri Sep 24, 2010 1:50 am**

It hides the x,y in the parent class, so you'd have to use the scope resolution operator to access them. vector2f::x and vector2f::y.

Elysian Shadows

storing return values then using vs using directly

storing return values then using vs using directly

Re: storing return values then using vs using directly

Re: storing return values then using vs using directly