Question

I have a class that has several member classes as attributes. The constructor of the class will take a filename of a byte file. The different member classes use subsequent parts of the file in their constructors, lets call them part A, B and C. The size of the file will vary.

Using the heap I would do something like this:

class myClass
{

    myClass(char *filename)
    {

        std::ifstream inputFile(filename, std::ios::binary);

        m_Class1 = new ClassA(inputFile); // read part A
        m_Class2 = new ClassB(inputFile); // read part B
        m_Class3 = new ClassC(inputFile); // read part C

        inputFile.close();
    }
}

I would like to do this on the stack instead of the heap.

Initialization lists come to mind, but for that I would have to waste time re-reading the redundant part of the inputfile to get to the part needed for each member class.

I don’t know if this is just a terrible approach (most likely), but does anyone have any suggestions towards accomplishing this effectively? Or suggestions for another way of organizing this?

Answer 1

class myClass {
    myClass(char *filename) : inputFile(filename, std::ios::binary),
                              m_Class1(inputFile),
                              m_Class2(inputFile),
                              m_Class3(inputFile) {
        inputFile.close();
    }

private:
    std::ifstream inputFile;
    ClassA m_Class1;
    ClassA m_Class2;
    ClassA m_Class3;

};

Note that the declaration order of the members is important.