静态线程函数访问非静态类成员在C++

Question

Class Test{ 
    int value; 
    static void* thread_func(void* args){ 
     value++; 
    } 
    void newthread(){ 
     pthread_create(&thread_func,...); 
    } 
} 

我试图创建Class Test.因此编译器会强迫一个线程我做thread_func静态的。但是，我无法再访问非静态成员“value”。它说：

invalid use of member 'Class::value' in static member function 

有没有办法解决它？

Answer 1

但是我不能访问非静态 成员“值”了。

那是因为在你的类static功能没有（和不能有）this指针。所有你需要的指针传递给Test对象pthread_create()功能第四参数，然后做到这一点：

static void* thread_func(void* args) 
{ 
     Test *test = static_cast<Test*>(args); 
     test->value++; 
     //write return statement properly 
} 

---

但是，如果你正在做的thread_func()太多的事情需要访问在很多地方Test类的成员，那么我建议这样的设计：

//this design simplifies the syntax to access the class members! 
class Test 
{ 
    //code omitted for brevity 

    static void* thread_func(void* args) 
    { 
      Test *test = static_cast<Test*>(args); 
      test->run(); //call the member function! 
      //write return statement properly 
    } 
    void run() //define a member function to run the thread! 
    { 
      value++;//now you can do this, because it is same as 'this->value++; 
      //you do have 'this' pointer here, as usual; 
      //so access other members like 'value++'. 
    } 
    //code omitted for brevity 
    } 

---

更好的设计：定义一个可重用的类！

甚至更​​好的是定义与纯虚拟函数run()一个可重复使用的类由派生类来实现。这是它应该如何设计：

//runnable is reusable class. All thread classes must derive from it! 
class runnable 
{ 
public: 
    virtual ~runnable() {} 
    static void run_thread(void *args) 
    { 
     runnable *prunnable = static_cast<runnable*>(args); 
     prunnable->run(); 
    } 
protected: 
    virtual void run() = 0; //derived class must implement this! 
}; 

class Test : public runnable //derived from runnable! 
{ 
public: 
    void newthread() 
    { 
     //note &runnable::run_thread 
     pthread_create(&runnable::run_thread,..., this); 
    } 
protected: 
    void run() //implementing the virtual function! 
    { 
     value++; // your thread function! 
    } 
} 

看起来更好？

Answer 2

让thread_func将一个指向该类的对象的指针作为参数。

static void* thread_func(void* pThis) 
{ 
    static_cast<Test*>(pThis)->value++; 
} 

在的情况下，这种方法要采取一些其他的信息，以及，把双方在另一个struct/class和传递英寸