返回管理this的shared_ptr

通過(guò)wek_ptr返回管理this資源的共享智能指針對(duì)象shared_ptr。C++11中為我們提供了一個(gè)模板類叫做std::enable_shared_from_this，這個(gè)類中有一個(gè)方法叫做shared_from_this()，通過(guò)這個(gè)方法可以返回一個(gè)共享智能指針，在函數(shù)的內(nèi)部就是使用weak_ptr來(lái)監(jiān)測(cè)this對(duì)象，并通過(guò)調(diào)用weak_ptr的lock()方法返回一個(gè)shared_ptr對(duì)象。

#include <iostream>
#include <memory>
using namespace std;struct Test : public enable_shared_from_this<Test>
{shared_ptr<Test> getSharedPtr(){return shared_from_this();}~Test(){cout << "class Test is disstruct ..." << endl;}
};int main()
{shared_ptr<Test> sp1(new Test);cout << "use_count: " << sp1.use_count() << endl;shared_ptr<Test> sp2 = sp1->getSharedPtr();cout << "use_count: " << sp1.use_count() << endl;return 0;
}

循環(huán)引用的案例

#include <iostream>
#include <memory>
using namespace std;struct TA;
struct TB;struct TA
{shared_ptr<TB> bptr;~TA(){cout << "class TA is disstruct ..." << endl;}
};struct TB
{shared_ptr<TA> aptr;~TB(){cout << "class TB is disstruct ..." << endl;}
};void testPtr()
{shared_ptr<TA> ap(new TA);shared_ptr<TB> bp(new TB);cout << "TA object use_count: " << ap.use_count() << endl;cout << "TB object use_count: " << bp.use_count() << endl;ap->bptr = bp;bp->aptr = ap;cout << "TA object use_count: " << ap.use_count() << endl;cout << "TB object use_count: " << bp.use_count() << endl;
}int main()
{testPtr();return 0;
}

修改

#include <iostream>
#include <memory>
using namespace std;struct TA;
struct TB;struct TA
{weak_ptr<TB> bptr;~TA(){cout << "class TA is disstruct ..." << endl;}
};struct TB
{shared_ptr<TA> aptr;~TB(){cout << "class TB is disstruct ..." << endl;}
};void testPtr()
{shared_ptr<TA> ap(new TA);shared_ptr<TB> bp(new TB);cout << "TA object use_count: " << ap.use_count() << endl;cout << "TB object use_count: " << bp.use_count() << endl;ap->bptr = bp;bp->aptr = ap;cout << "TA object use_count: " << ap.use_count() << endl;cout << "TB object use_count: " << bp.use_count() << endl;
}int main()
{testPtr();return 0;
}