在C ++中我做了一个函数调用4个threads.in函数有一个int值我怎么能在另一个函数中使用它 [英] In C++ I made a funcion call as 4 threads.in that funcion there is an int value how can I use it in another function

问题描述

cv::VideoCapture a;
	cv::VideoCapture b;
	cv::VideoCapture c;
	cv::VideoCapture d;
	a.open("traffic1.mp4");
	b.open("traffic2.mp4");
	c.open("traffic3.mp4");
	d.open("traffic4.mp4");
	std::thread t1 (traffic,a,"a");
	std::thread t2 (traffic, b, "b");
	std::thread t3(traffic, c, "c");
	std::thread t4(traffic, d, "d");
	t1.join();
	t2.join();
	t3.join();
	t4.join();

这里的函数流量（）有一个整数值我怎样才能访问它什么是语法



我尝试了什么：



i没有得到任何语法的

here in function traffic() there is a integer value how can i access it what is the syntax

What I have tried:

i did't get any syntax for this

推荐答案

要在其他函数中使用，必须声明一个全局变量。你可以使用普通的int 外部交通功能。



但我认为这是一个主要的缺陷，你有不同的线程访问相同的变量如果变量不是所有线程的常量。



不清楚哪个线程赢得了访问竞争。所以最好用一些同步代码编写一个getInteger（）和setInteger（）函数。



请阅读文章 C ++ 11线程，锁和条件变量，以便更好地理解陷阱和解决方案。

For use in other functions you must declare a global variable. You can use a normal int outside the traffic function.

But I would call it a major flaw that you have different threads accessing the same variable if the variable isnt constant for all threads .

It is not clear which thread wins the race for access. So it is better to write an getInteger() and setInteger() function with some syncronization code.

Please read the article C++11 threads, locks and condition variables for better understanding the pitfalls and solutions.

这篇关于在C ++中我做了一个函数调用4个threads.in函数有一个int值我怎么能在另一个函数中使用它的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！