关于智能指针的问题,有时候为了方便,需要在析构时附加一些清理操作,或者,有的指针本身来自C的库文件中,这时候,就非常期望能够使用自定义的deleter,
但是标准C++创建函数如std::make_unique / std::make_shared 等不支持创建带有自定义deleter的智能指针,这时,我们只能使用自己的办法,
#include <memory>
#include <iostream>
class myclass {
public:
myclass() {
std::cout << "myclass" << std::endl;
}
~myclass() {
std::cout << "~myclass" << std::endl;
}
void doSomething() {
std::cout << "myclass is doing something" << std::endl;
}
};
class A {
public:
A(){
std::cout << "A" << std::endl;
}
~A(){
std::cout << "~A" << std::endl;
}
void doSomething() {
std::cout << "A is doing something" << std::endl;
}
};
struct my_creator_s {
myclass* p = new myclass();
A* a = new A();
};
struct my_deleter_s {
void operator()(myclass* p) { delete p; }
};
struct my_deleter_s2 {
void operator()(my_creator_s* s) { delete s->p; delete s->a; }
};
myclass* mycreator() {
return new myclass();
}
void mydeleter(myclass* p){
delete p;
};
int Test1() {
std::cout << "----------------------------Test Method 1-----------------------------" << std::endl;
myclass* myptr = new myclass;
std::unique_ptr<myclass, decltype(&mydeleter)> ptr{ myptr, &mydeleter };
ptr->doSomething();
return 0;
}
int Test2() {
std::cout << "----------------------------Test Method 2-----------------------------" << std::endl;
std::unique_ptr<myclass, my_deleter_s> ptr2 = std::unique_ptr<myclass, my_deleter_s>(new myclass(), my_deleter_s());
ptr2.get()->doSomething();
return 0;
}
int Test3() {
std::cout << "----------------------------Test Method 3-----------------------------" << std::endl;
std::unique_ptr<my_creator_s, my_deleter_s2> ptr3 = std::unique_ptr<my_creator_s, my_deleter_s2>(new my_creator_s(), my_deleter_s2());
ptr3.get()->a->doSomething();
return 0;
}
int main() {
Test1();
Test2();
Test3();
return 0;
}
这段代码的输出如下,
----------------------------Test Method 1-----------------------------
myclass
myclass is doing something
~myclass
----------------------------Test Method 2-----------------------------
myclass
myclass is doing something
~myclass
----------------------------Test Method 3-----------------------------
myclass
A
A is doing something
~myclass
~A
说明:这里写了两个creator,函数mycreator没有用到;deleter一个采用了struct的办法,一个是采用了void函数的办法,大家可以自己尝试; 对于需要同时处理多个参数或变量的形式,建议采用struct或class的形式,Test Method3展示了如何使用creator或者说constructor创建的办法,写成这种方式是因为智能指针的deleter中只接受一个参数,例如,不能写成这样的,
struct my_deleter_s2 {
void operator()(myclass* p, A* a) { delete p; delete a; }
};
参考附录:
Custom Deleter for C++ Smart Pointers - Lei Mao's Log Book文章来源:https://www.toymoban.com/news/detail-731892.html
本文结束文章来源地址https://www.toymoban.com/news/detail-731892.html
到了这里,关于C++11补充:智能指针如std::unique_ptr如何添加自定义的deleter的文章就介绍完了。如果您还想了解更多内容,请在右上角搜索TOY模板网以前的文章或继续浏览下面的相关文章,希望大家以后多多支持TOY模板网!