错误:变量“无法隐式捕获,因为未指定默认捕获模式"
我正在尝试遵循这个例子使用带有 remove_if
的 lambda.这是我的尝试:
I am trying to follow this example to use a lambda with remove_if
. Here is my attempt:
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());
但这无法编译:
error C3493: 'flagId' cannot be implicitly captured because no default capture mode has been specified
如何在 lambda 表达式中包含外部参数 flagId
?
How can I include the outside parameter, flagId
, in the lambda expression?
推荐答案
您必须指定要捕获的 flagId
.这就是 []
部分的用途.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).类似的东西:
You must specify flagId
to 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:
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[&flagId](Flag& device)
{ return device.getId() == flagId; });
通过引用捕获.如果你想通过 const 值捕获,你可以这样做:
Which captures by reference. If you want to capture by const value, you can do this:
auto new_end = std::remove_if(m_FinalFlagsVec.begin(), m_FinalFlagsVec.end(),
[flagId](Flag& device)
{ return device.getId() == flagId; });
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; });
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:
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:
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
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