C++ 错误：变量“无法隐式捕获，因为未指定默认捕获模式”
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Error: variable "cannot be implicitly captured because no default capture mode has been specified"
提问by user63898
I am trying to follow this exampleto use a lambda with remove_if. Here is my attempt:
我正在尝试按照此示例将 lambda 与remove_if. 这是我的尝试：
int flagId = _ChildToRemove->getId();
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[](Flag& device) {
return device.getId() == flagId;
});
m_FinalFlagsVec.erase(new_end, m_FinalFlagsVec.end());
but this fails to compile:
但这无法编译：
error C3493: 'flagId' cannot be implicitly captured because no default capture mode has been specified
How can I include the outside parameter, flagId, in the lambda expression?
如何flagId在 lambda 表达式中包含外部参数 , ？
回答by AndyG
You must specify flagIdto be captured. That is what the []part is for. Right now it doesn't capture anything. You can capture (more info) by value or by reference. Something like:
您必须指定flagId被捕获。这就是[]零件的用途。现在它没有捕获任何东西。您可以按值或按引用捕获（更多信息）。就像是：
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[&flagId](Flag& device)
{ return device.getId() == flagId; });
Which captures by reference. If you want to capture by const value, you can do this:
通过引用捕获。如果你想通过 const 值捕获，你可以这样做：
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[flagId](Flag& device)
{ return device.getId() == flagId; });
Or by mutable value:
或者通过可变值：
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[flagId](Flag& device) mutable
{ return device.getId() == flagId; });
Sadly there is no straightforward way to capture by const reference. I personally would just declare a temporary const ref and capture that by ref:
遗憾的是，没有直接的方法可以通过常量引用进行捕获。我个人只会声明一个临时的 const ref 并通过 ref 捕获它：
const auto& tmp = flagId;
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[&tmp](Flag& device)
{ return device.getId() == tmp; }); //tmp is immutable
