boost circular_buffer控股指针

Question

有没有一种方法可以确保我的对象在循环缓冲区中被覆盖之前被删除？这里有一些代码来说明我的问题。

boost::circular_buffer<MyObject*> cBuf(5); 
cBuf.push_back(new MyObject()); // cBuf[0] 
cBuf.push_back(new MyObject()); // cBuf[1] 
cBuf.push_back(new MyObject()); // cBuf[2] 
cBuf.push_back(new MyObject()); // cBuf[3] 
cBuf.push_back(new MyObject()); // cBuf[4] 

// before this overwrite occurs, how do i make sure the pointer 
// position cBuf[0] is deleted? 
cBuf.push_back(new MyObject()); // this will overwrite position 0 

Answer 1

这是智能指针的经典场景。任何智能指针。

最简单的选择将标准::的unique_ptr：

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#include <boost/circular_buffer.hpp> 
#include <iostream> 

struct MyObject { 
    MyObject(int i) : _i(i) { std::cout << __FUNCTION__ << " _i=" << _i << "\n"; } 
    ~MyObject()    { std::cout << __FUNCTION__ << " _i=" << _i << "\n"; } 
    int _i; 
}; 

int main() { 
    using Ptr = std::unique_ptr<MyObject>; 
    boost::circular_buffer<Ptr> cBuf(5); 
    cBuf.push_back(std::make_unique<MyObject>(0)); // cBuf[0] 
    cBuf.push_back(std::make_unique<MyObject>(1)); // cBuf[1] 
    cBuf.push_back(std::make_unique<MyObject>(2)); // cBuf[2] 
    cBuf.push_back(std::make_unique<MyObject>(3)); // cBuf[3] 
    cBuf.push_back(std::make_unique<MyObject>(4)); // cBuf[4] 

    std::cout << "Full, pushing extra\n"; 

    cBuf.push_back(std::make_unique<MyObject>(5)); // this will overwrite position 0 

    std::cout << "Done\n"; 
} 

打印：

MyObject::MyObject _i=0 
MyObject::MyObject _i=1 
MyObject::MyObject _i=2 
MyObject::MyObject _i=3 
MyObject::MyObject _i=4 
Full, pushing extra 
MyObject::MyObject _i=5 
MyObject::~MyObject _i=0 
Done 
MyObject::~MyObject _i=1 
MyObject::~MyObject _i=2 
MyObject::~MyObject _i=3 
MyObject::~MyObject _i=4 
MyObject::~MyObject _i=5