How to initialize an array of objects of a parameterized constructor

Question

I need to initialize an array of objects of a parametrized constructor . How can i do it in best possible way ?

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Answer 1

Note that malloc does not construct objects, and so calling a1[i]=a2 is bad form. It probably seems to work fine since they are POD-ish objects, but this is not the proper way to do C++. It is undefined behavior, which is completely unpredictable. It may work ten thousand times in a row, and then erase your bank account. You should use new instead, which also constructs. Or better yet, use a vector, like the other answers suggest. Also, be sure that the default constructor initializes the data, and initialization will be less of a worry.

If you really must use malloc, the "correct way" to initialize is this:

std::uninitialized_copy(a1, a1+10, a2); //constructs and assigns

which is roughly equivalent to:

{
    int i=0;
    try {
        for(i=0; i<10; ++i)
           new(a1+i)A(a2); //constructs and initializes in the buffer
    } catch(...) { 
        try {
            for(; i>=0; --i)
               (a1+i)->~A(); //destroy if an error occured
        } catch(...) { 
            std::terminate();
        }
        throw;
    }
}