将lambdas传递给std :: thread和调用类方法 [英] Passing lambdas to std::thread and calling class methods

问题描述

我有一个麻烦使用std :: thread和lambdas。我有一个方法TheMethod，我应该使用std :: thread并行化一些函数调用到同一个类中的方法。

I'm having a bit of trouble using std::thread together with lambdas. I have a method TheMethod where I should use std::thread to parallelize some function calls to methods in the same class.

我定义一个lambda函数，并尝试传递它如下面的std ::线程实例我创建：

I define a lambda function, and try to pass it as follows to the std::thread instance I create:

auto functor = 
   [this](const Cursor& c, size_t& result) ->void {result = classMethod(c);};

size_t a;
Cursor cursor = someCursor();

std::thread t1(functor, cursor, a);

t1.join();

不幸的是，编译器给了我：

Unfortunately, the compiler gives me:

  /usr/include/c++/4.8/functional:1697:61: error: no type named ‘type’ in ‘class std::result_of<TheMethod...

我在lambda定义中尝试了很多组合，并且在调用std :: thread构造函数的方式，总是得到相同的错误。

I tried a lot of combinations in the lambda definition, and in the way of calling the std::thread constructor, but I get the same error always. The thread library is included, I link pthread too.

感谢提示！

推荐答案

您可以使用std :: ref通过引用传递参数：

You can use std::ref to pass the parameters by reference:

std::thread t1(functor, std::ref(cursor), std::ref(a))

参数在lambda本身的参数：

You could also capture the parameters by reference in the lambda itself:

size_t a;
Cursor cursor = someCursor();
std::thread t1([&] {a = classMethod(cursor);});
t1.join();

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