Question

everyone! I am new for C++ and now work on a C++ project.The whole structure has been completed.But I have been wondering about

how to build the vector of different objects and how to read the file since the beginning.

In my problem, first I have to read a txt file with readObstacles(std::istream &fs) that has the following format:

RECTANGLE 1 2.5 2 2 0.2
CIRCLE 1 2.5 1.2
RECTANGLE 4 2 2 2 0.3

(each obstacle begins a new line)

I need to read the data information of different obstacles and store these obstacles in a vector.
Class Obstacle is the base class with two sub-classes CIRCLE and RECTANGLE.
I try to put the these different obstacles (that i think should have their data info) in a obstacle vector and then call the virtual function they both have.

Below is the code I try to do with:

vector<Obstacle> obsdata; 

Myworld::readObstacles(std::istream &fs)
{
    std::string shape;
    double num1,num2,num3,num4,num5;
    while(fs>>shape>>num1>>num2>>num3>>num4>>num5)
    {
        if(shape=="CIRCLE") {
            CIRCLE c;
            c.m_Xc=num1;
            c.m_Yc=num2;
            c.m_Radius=num3;       
            obsdata.push_back(c);
        }

        if(shape=="RECTANGLE") {
            RECTANGLE r;
            r.center_x=num1;
            r.center_y=num2;    
            r.width=num3;
            r.height=num4;
            r.angle=num5;
            obsdata.push_back(r);
        }
    }
}

MyWorld::writeMatlabDisplayCode(std::ostream &fs)
{
    for( i = 0; i < obsdata.size(); i++ )
        obsdata[i].writeMatlabDisplayCode(fs);
}

I know it doesn’t work but i don’t know what i should do.

Any words will help. Thanks !

Answer 1

You could try just reading the whole line at a time then tokenize the values…

vector<Obstacle*> obsdata;

string line;
while(getline(fs, line)) {
    char *token = strtok(line.c_str(), " ");
    string shape(token);

    vector<double> numbers;
    stringstream ss;
    while(token = strtok(NULL, " ")) {
        double d;
        ss << token;
        ss >> d;

        numbers.push_back(d);
    }

    if(shape == "CIRCLE") {
        CIRCLE *c = new CIRCLE();
        c->m_Xc=numbers[0];
        c->m_Yc=numbers[1];
        c->m_Radius=numbers[2];       
        obsdata.push_back(c);
    } else if(shape == "RECTANGLE") {
        RECTANGLE *r = new RECTANGLE();
        r->center_x=numbers[0];
        r->center_y=numbers[1];    
        r->width=numbers[2];
        r->height=numbers[3];
        r->angle=numbers[4];
        obsdata.push_back(r);
    }
}

I would delete this vector of pointers in your MyWorld destructor:

~MyWorld() {
    // loop thanks to gf
    for(std::vector<Obstacle*>::iterator it = obsdata.begin(); it != obsdata.end(); ++it)
        delete *it;  
}