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POdelayed initialization?
 

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    <p>could somebody please explain why this happens? I have written the following:</p> <p>1) a WindowManager class which is implemented as a singleton and has an <code>Instance()</code> method, defined like so:</p> <pre><code>static WindowManager * instance_; //... WindowManager * WindowManager::instance_ = 0; WindowManager &amp; WindowManager::Instance() { if (!instance_) instance_ = new WindowManager(); return *instance_; } </code></pre> <p>2) a <code>WindowManager::createWindow</code> method that returns a reference to a newly created window, defined like so:</p> <pre><code>Window &amp; WindowManager::createWindow() { windows_.push_back(Window()); return windows_.at(windows_.size() - 1); } </code></pre> <p>3) a <code>Window::print</code> method that prints a message inside the window</p> <p>In my main program, I have written the following:</p> <pre><code>ui::Window &amp; win1 = ui::WindowManager::Instance().createWindow(); ui::Window &amp; win2 = ui::WindowManager::Instance().createWindow(); win1.print("First window"); win2.print("Second window"); </code></pre> <p>This does not work! Only the second call to <code>print</code> is executed (for <code>win2</code>). However, if I change the order, like so:</p> <pre><code>ui::Window &amp; win1 = ui::WindowManager::Instance().createWindow(); win1.print("First window"); ui::Window &amp; win2 = ui::WindowManager::Instance().createWindow(); win2.print("Second window"); </code></pre> <p>then everything works as expected. If anybody could shed some light on this situation, any help would be greatly appreciated.</p>
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    1. USDan Nestor
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    1. COThe problem was that in `createWindow` I return a reference to an object created on the stack, which is destroyed when the method ends. Changing `windows_` from `std::vector<Window>` to `std::vector<Window *>` and modifying everything else accordingly solved my problem.
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      1. USDan Nestor
    2. COThats not your cause, but that would solve the real problem
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      1. USMooing Duck
    3. COPlease read this: http://stackoverflow.com/questions/1008019/c-singleton-design-pattern/1008289#1008289
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      1. USMartin York
 

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