使用自定義刪除器中的shared_ptr

Question

我定義一個類，它有一個成員模板，到位的std :: shared_ptr的默認缺失者的：

class DebugDelete { 
    public: 
     DebugDelete(std::ostream &s = std::cerr): os(s) { } 
     // as with any function template, the type of T is deduced by the compiler 
     template <typename T> void operator()(T *p) const 
     { 
      os << "deleting unique_ptr" << std::endl; 
      delete p; 
     } 
    private: 
     std::ostream &os; 
}; 

當我將它應用於下面的代碼，一些報告錯誤：

class A { 
    public: 
     // [Error] class 'A' does not have any field named 'r' 
     A(std::shared_ptr<std::set<int>> p): r(p) { } // 1: How can I use self-defined deleter to initialize r in constructor 
     A(int i): s(new std::set<int>, DebugDelete()) { } // 2: OK, what is the difference between this constructor and 3 
    private: 
     // [Error] expected identifier before 'new' 
     // [Error] expected ',' or '...' before 'new' 
     std::shared_ptr<std::set<int>> r(new std::set<int>, DebugDelete()); // 3: error 
     std::shared_ptr<std::set<int>> s; 
}; 

Answer 1

在initialize_list您可以使用自定義刪除器一樣

shared_ptr<set<int>> r = shared_ptr<set<int>>(new set<int>, DebugDelete()); 

一nd你不應該使用一個shared_ptr來初始化另一個shared_ptr。