boost circular_buffer控股指針

Question

有沒有一種方法可以確保我的對象在循環緩衝區中被覆蓋之前被刪除？這裏有一些代碼來說明我的問題。

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

這是智能指針的經典場景。任何智能指針。

最簡單的選擇將標準::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