37 lines
1 KiB
Markdown
37 lines
1 KiB
Markdown
[< Back](../README.md)
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# Exercise: Play with parameter passing
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In this exercise we will look together at what happens when we change a reference
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parameter to a value or a const reference.
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Let's look at this function in [`Game.cpp`](../../../lib/Game.cpp)
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```cpp
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void Game::processEvents(InputState & inputState) {
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auto event = canvas.pollEvent();
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if (event && event.value().type == sf::Event::Closed) {
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inputState.close = true;
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return;
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}
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inputState.down = sf::Keyboard::isKeyPressed(sf::Keyboard::Key::Down);
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inputState.up = sf::Keyboard::isKeyPressed(sf::Keyboard::Key::Up);
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inputState.left = sf::Keyboard::isKeyPressed(sf::Keyboard::Key::Left);
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inputState.right = sf::Keyboard::isKeyPressed(sf::Keyboard::Key::Right);
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}
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```
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## Exercise
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You can follow along locally:
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1. Make `inputState` a value. What happens when you compile the code? Can you explain why?
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2. Now make it a `const` reference. What happens? Can you explain why?
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3. Revert it back to a non-const reference an make sure the code compile.
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