如何在线程池中用lambda调用类的成员函数实现疑问？
摘要：1.QThreadPool的基础使用 1.1 引入相关头文件QThreadPool和QRunnable #include <QRunnable> #include <QThr
1.QThreadPool的基础使用
1.1 引入相关头文件QThreadPool和QRunnable
#include <QRunnable>
#include <QThreadPool>
1.2 QThreadPool
创建一个线程池一般有两种方法，第一种使用全局线程池
QThreadPool *pool = QThreadPool::globalInstance();
第二种，新建一个线程池，请记住最好设置一些常用的属性
QThreadPool *pool= new QThreadPool();
//最大线程个数：4
pool->setMaxThreadCount(4);
1.3 QRunnable
QRunnable需要自己派生出一个具体的类，然后必须重写run函数（类似于QThread），例如
class BTask : public QRunnable
{
public:
void run() override
{
std::cout<<"task running in thread pool"<<std::endl;
}
};
1.4 执行（task在默认情况下会由线程池尝试释放，无需手动delete）
BTask * task = new BTask();
pool->start(task);
//等待完成
pool->waitForDone();
2. 加入Lambda表达式
2.1 使用functional声明一个回调函数，样式为void xxxx();
#include <functional>
typedef std::function<void(void)> task_cb;
2.2 给BTask添加一个设置回调函数功能add，以下是完整的类
class BTask : public QRunnable
{
public:
void run() override
{
std::cout<<"task running in thread pool"<<std::endl;
if(call)
call();
}
void add(callback cb)
{
call = cb;
}
private:
callback call;
};
2.3 使用Lambda表达式实现回调函数,先实现一个A类，然后在A里创建线程池，创建BTask对象
class A
{
public:
A()
{
pool = new QThreadPool();
pool->setMaxThreadCount(4);
//pool = QThreadPool::globalInstance();
}
~A()
{
if(pool)
{
delete pool;
pool = nullptr;
}
}
void Do()
{
//auto delete task
BTask * task = new BTask();
//lambda
task->add([this](){
this->DoOther();
});
pool->start(task);
pool->waitForDone();
}
private:
void DoOther()
{
std::cout<<"do something"<<std::endl;
}
private:
QThreadPool *pool;
};
3.完整代码
完成函数调用
#include <QRunnable>
#include <QThreadPool>
#include <iostream>
typedef std::function<void(void)> callback;
class BTask : public QRunnable
{
public:
void run() override
{
std::cout<<"task running in thread pool"<<std::endl;
if(call)
call();
}
void add(callback cb)
{
call = cb;
}
private:
callback call;
};
class A
{
public:
A()
{
pool = new QThreadPool();
pool->setMaxThreadCount(4);
//pool = QThreadPool::globalInstance();
}
~A()
{
if(pool)
{
delete pool;
pool = nullptr;
}
}
void Do()
{
//auto delete task
BTask * task = new BTask();
task->add([this](){
this->DoOther();
});
pool->start(task);
pool->waitForDone();
}
private:
void DoOther()
{
std::cout<<"do something"<<std::endl;
}
private:
QThreadPool *pool;
};
int main(int argc, char *argv[])
{
A a;
a.Do();
std::cout<<"finished"<<std::endl;
return 0;
}