用foreach循环更新std :: list中的每个值C ++ [英] Update each value in a std::list with a foreach loop C++

问题描述

我在C ++中有一个 std :: list ，我正在尝试使用 for(类型t:列表)用于更新每个对象的值的操作.因此，我有一个称为球的列表，每个球都有一个位置.我的循环代码是:

I've got a std::list in C++ and I'm trying to use a for(Type t : list) operation to update the value of each object. So I have a list called balls and each ball has a position. My code to for the loop is:

for(OpenGLView::AssetInstance ball : balls)
            ball.position = calculateBallPosition(ball);

computeBallPosition取一个球并根据经过的时间返回其新位置.

where calculateBallPosition takes a ball and returns its new position based on time elapsed.

我遇到的问题是列表中元素的值似乎没有更新.当我在循环运行后检查它们的值时，它与以前一样.我猜我的错误是在理解此循环的工作方式，但我仍无法弄清楚如何解决它.

The problem I am running into is that the value of the elements in the list don't seem to be updating. When I check their values after the loop has run, it's the same as it was before. I'm guessing my mistake is in understanding the way this loop works, but I haven't been able to figure out how to fix it.

推荐答案

您正在复制原始对象，请使用引用

You're taking a copy of original object, use a reference

for(OpenGLView::AssetInstance& ball : balls)
            ball.position = calculateBallPosition(ball);

或者简单地

for( auto& ball : balls)
            ball.position = calculateBallPosition(ball);

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