class 变量中的 list/vector 个 class 方法

Question

我需要维护一个方法列表，这些方法将以不同的顺序执行以进行测试。我们正在从 C 转向 C++ 以使用 google 框架。是否可以维护一个指向一些 class 方法的函数指针列表以用于在 class 中执行，以便它们可以在实例化后使用？请参考http://cpp.sh/265y

#include <iostream>
#include <string>
#include <vector>
using namespace std;

typedef void (*funcType)();

class Sample {
    public:
    vector<funcType> func_list;

    Sample();

    void formList();
    void method1();
    void method2();
    void method3();    
};

void Sample::formList() {
    func_list.push_back(&method1);
    func_list.push_back(&method2);
    func_list.push_back(&method3);
}

void Sample::method1 () {
    cout << "method1" << endl;
}

void Sample::method2 () {
    cout << "method2" << endl;
}

void Sample::method3 () {
    cout << "method3" << endl;
}

int main()
{
    Sample sample; //* = new Sample();
    sample.formList();
    vector<funcType>::iterator it;
    for (it = sample.func_list.begin(); it != sample.func_list.end(); ++it) {
         ((*it));
    }

}

答案：http://cpp.sh/8rr2

Answer 1

简介

您当前已将 funcType 声明为 void(*)() 的别名，它是指向某个不带参数且 returns 无效的函数的指针。您应该使用的是指向成员函数的指针，因为这将适合您尝试调用的实体。

class Sample;
typedef void (Sample::*funcType)();

你还必须限定你的成员函数，当你要获取他们的地址时：

void Sample::formList() {
    func_list.push_back(&Sample::method1);
    func_list.push_back(&Sample::method2);
    func_list.push_back(&Sample::method3);
}

当调用一个成员函数时，你需要一个你想在其上调用它的对象，这意味着你——为了通过指向成员的指针调用一个成员函数-function—必须在调用点提供一个对象。

for (it = sample.func_list.begin(); it != sample.func_list.end(); ++it) {
     (sample.*(*it)) (); // invoke the member-function referred to by `it`
}                        // on the object named `sample`

进一步阅读

whosebug.com - Calling member-function pointer
cppreference.com - Pointers to member functions

实施示例

#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Sample;
typedef void (Sample::*funcType)();

class Sample {
  public:
    vector<funcType> func_list;

    void formList();
    void method1();
    void method2();
    void method3();    
};

void Sample::formList() {
  func_list.push_back(&Sample::method1);
  func_list.push_back(&Sample::method2);
  func_list.push_back(&Sample::method3);
}

void Sample::method1 () {
  cout << "method1" << endl;
}

void Sample::method2 () {
  cout << "method2" << endl;
}

void Sample::method3 () {
  cout << "method3" << endl;
}

int main()
{
  Sample sample; //* = new Sample();
  sample.formList();
  vector<funcType>::iterator it;
  for (it = sample.func_list.begin(); it != sample.func_list.end(); ++it) {
    (sample.*(*it)) ();
  }
}

method1
method2
method3

Answer 2

您可以使用可怕的成员函数指针语法：

Live On Coliru

// Example program
#include <iostream>
#include <string>
#include <vector>
using namespace std;

class Sample;

typedef void (Sample::*funcType)();

class Sample {
  public:
    vector<funcType> func_list;

    Sample(){}

    void formList();
    void method1();
    void method2();
    void method3();
};

void Sample::formList() {
    func_list.push_back(&Sample::method1);
    func_list.push_back(&Sample::method2);
    func_list.push_back(&Sample::method3);
}

void Sample::method1() { cout << "method1" << endl; }

void Sample::method2() { cout << "method2" << endl; }

void Sample::method3() { cout << "method3" << endl; }

int main() {
    Sample sample; //* = new Sample();
    sample.formList();
    vector<funcType>::iterator it;
    for (it = sample.func_list.begin(); it != sample.func_list.end(); ++it) {
        (sample.*(*it))(); // HORRIFIC, INNIT? SEE BELOW FOR BETTER
    }
}

好多了：

但是，您可以使用 C++11/TR1 std::function<> 或 boost::function<>:

typedef function<void(Sample*)> funcType;

// ...
func_list.push_back(mem_fn(&Sample::method1));
func_list.push_back(mem_fn(&Sample::method2));
func_list.push_back(mem_fn(&Sample::method3));

也看到了Live On Coliru

for (it = sample.func_list.begin(); it != sample.func_list.end(); ++it) {
    (*it)(&sample); // much better
}

The added versatility is mainly in that you can cater for different signatures: Live On Coliru

class Sample {
  public:
    vector<funcType> func_list;

    Sample(){}

    void formList();
    void method1(int);
    void method2(std::string);
    void method3(double, double, double);
};

void Sample::formList() {
    using std::placeholders::_1;
    func_list.push_back(bind(&Sample::method1, _1, 42));
    func_list.push_back(bind(&Sample::method2, _1, "Hello world"));
    func_list.push_back(bind(&Sample::method3, _1, 1, 2, 3));
}

class 变量中的 list/vector 个 class 方法

list/vector of class methods in a class variable

c++

function-pointers

class

vector

class-method

简介

实施示例

好多了：