将具有相反操作数的两个函数重构为一个

Question

I would like to refactor the following 2 functions so that the logic will be in one function with one parameter:

void zoom_in() {
  object.zoom_factor *= 2;
  object.width /= 2;
  object.height /= 2;
}

void zoom_out() {
  object.zoom_factor /= 2;
  object.width *= 2;
  object.height *= 2;
}

What I tried to do:

void zoom_in() {
  zoom_helper(true);
}

void zoom_out() {
  zoom_helper(false);
}

void zoom_helper(bool in) {
  float factor = (in ? 2 : .5);
  object.zoom_factor *= factor;
  object.width /= factor;
  object.height /= factor;
}

However I would rather have the factor be an int . Can I cleanly refactor this code?

Answer 1

You can use an array of function objects:

void zoom_helper(bool in) {
    static const std::function<void(int&)> mul = [](int& x) { x *= 2; };
    static const std::function<void(int&)> div = [](int& x) { x /= 2; };
    static const auto update[2] = { div, mul };
    update[in](object.zoom_factor);
    update[!in](object.width);
    update[!in](object.height);
}

I don't think this is much of a benefit though, and I would not personally write this except for fun.

Answer 2

The simplest way to refactor is just using an if ... else block:

void zoom_helper(bool in) {
    if (in) {
        object.zoom_factor *= 2;
        object.byte_aligned_columns /= 2;
        object.rows /= 2;
    }
    else {
        object.zoom_factor /= 2;
        object.byte_aligned_columns *= 2;
        object.rows *= 2;
    }
}

But maybe you're looking for something more 'elegant' or 'clever'?