std::remove_if - lambda，不从集合中删除任何内容 [英] std::remove_if - lambda, not removing anything from the collection

问题描述

好吧，我想我在这里犯了一个愚蠢的错误.我有一个 DisplayDevice3d 列表，每个 DisplayDevice3d 都包含一个 DisplayMode3d 列表.我想从 DisplayDevice3d 列表中删除所有没有任何 DisplayMode3d 的项目.我正在尝试使用 Lambda 来做到这一点，即:

Ok, I expect I've made a dumb mistake here. I have a list of DisplayDevice3d and each DisplayDevice3d contains a list of DisplayMode3d. I want to remove all items from the list of DisplayDevice3d that don't have any DisplayMode3d's. I'm trying to use a Lambda to do it, ie.:

    // If the device doesn't have any modes, remove it.

  std::remove_if(MyDisplayDevices.begin(), MyDisplayDevices.end(),
   [](DisplayDevice3d& device) 
   { 
    return device.Modes.size() == 0; 
   }
  ); 

即使在 MyDisplayDevices 中的 6 个 DisplayMode3d 中，只有 1 个在其 Modes 集合中有任何 DisplayMode3d，但没有从列表中删除任何内容.

Even though out of 6 DisplayMode3d's in MyDisplayDevices, only 1 has any DisplayMode3d's in its Modes collection, nothing is being removed from the list.

我在这里犯了什么大错?

What numpty mistake have I made here?

好吧，我的错误是我应该使用 MyDisplayDevices.remove_if 而不是 std::remove_if，但是下面的答案对于使用 std::remove_if :p 是正确的.

Ah ok, my mistake was I should be using MyDisplayDevices.remove_if instead of std::remove_if, however the answers below are correct for use of std::remove_if :p.

MyDisplayDevices.remove_if( [](DisplayDevice3d const & device) 
                            { 
                                return device.Modes.size() == 0; 
                            });

推荐答案

你需要对 remove_if 返回的迭代器调用erase，它应该是这样的:

You need to call erase on the iterator returned from remove_if, It should look something like this:

auto new_end = std::remove_if(MyDisplayDevices.begin(), MyDisplayDevices.end(),
                              [](const DisplayDevice3d& device)
                              { return device.Modes.size() == 0; });

MyDisplayDevices.erase(new_end, MyDisplayDevices.end());

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