[英]How to access class member and methods from static method(signal handler)
[英]Initialising static member class ( for a signal handler )
在使用静态成员之前,我将像在此示例中一样初始化它们。
我想在我的代码中做同样的事情。 但它不起作用。 GCC告诉我: undefined reference to MainClass::TheStatic1
码:
#include <iostream>
using namespace std;
基类构造函数在给定Argument的'a'中
class MyStaticBase {
public:
MyStaticBase(int iSetA):a(iSetA){};
~MyStaticBase(){}
int a;
void SayHello(){
std::cout << "Say Hello from Static Instance: " << a << std::endl;
}
};
派生类使用其特定值初始化Base类。
// First derived Class
class MyStaticDerived1:public MyStaticBase{
public:
MyStaticDerived1():MyStaticBase(1){ }
};
// Second derived Class
class MyStaticDerived2:public MyStaticBase{
public:
MyStaticDerived2():MyStaticBase(2){}
};
包含两个类似的成员,只有它们是从基类派生的构造函数调用才有区别。
class MainClass {
public:
MainClass(){};
~MainClass(){};
static MyStaticDerived1 TheStatic1;
static MyStaticDerived2 TheStatic2;
};
主要的
int main() {
MainClass TheMainClass;
// [PROBLEM]: gcc:undefined reference to `MainClass::TheStatic1'
TheMainClass.TheStatic1.SayHello();
TheMainClass.TheStatic2.SayHello();
}
尝试在main()中解决(jap,其中一些只是猜测)
// Attempts:
// MyStaticDerived1::MyStaticDerived1(); // error: cannot call constructor ‘MyStaticDerived1::MyStaticDerived1’ directly [-fpermissive]
// MainClass::TheStatic1 TheStatic1; //error: expected ‘;’ before ‘TheStatic1’
// MainClass::TheStatic2 TheStatic2 = 0;
// MainClass::TheStatic1();
// MyStaticDerived1 MainClass::TheStatic1; //qualified-id in declaration before ‘;’ token
// MyStaticDerived1 MainClass::TheStatic1{}; //qualified-id in declaration before ‘{’ token
为什么我这样做?
MyStaticDerived是线程处理类,由信号处理程序(SIGCHILD)调用。 此处理程序只能访问静态成员。 管理两组进程,因此我需要两个类似的线程处理类。
复制粘贴代码以获取工作示例。 感谢@ThomasMatthews和@ user4581301使这个答案成为可能。 请参阅主函数上方的解决方案。 Futur信息请在@ThomasMatthews提供的链接中找到。
#include <iostream>
using namespace std;
class MyStaticBase {
public:
MyStaticBase(int iSetA):a(iSetA){};
~MyStaticBase(){}
int a;
void SayHello(){
std::cout << "Keep a signalhandler SHORT\n"
<< "Just set a flag =)\n"
<< "thx to all!\n"
<< " Instance: " << a << std::endl;
}
};
// Derived Classes
class MyStaticDerived1:public MyStaticBase{
public:
MyStaticDerived1():MyStaticBase(1){ }
};
class MyStaticDerived2:public MyStaticBase{
public:
MyStaticDerived2():MyStaticBase(2){}
};
class MainClass {
public:
MainClass(){};
~MainClass(){};
static MyStaticDerived1 TheStatic1;
static MyStaticDerived2 TheStatic2;
};
// [ Solution ]
MyStaticDerived1 MainClass::TheStatic1;
MyStaticDerived2 MainClass::TheStatic2;
int main() {
MainClass TheMainClass;
TheMainClass.TheStatic1.SayHello();
TheMainClass.TheStatic2.SayHello();
}
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