为什么我的类字段在构造函数中被销毁(Why my class field is destroyed in constructor)

 在我的构造函数中，我初始化一个字段。 初始化后，该字段将被销毁。 这是我的代码和我的测试： 
 
 A.hpp 
 
class A {
    private:
        T t;

    public:
    A(); 
    ~A();

    void add(string name, string num);
}; 
 
 A.cpp 
 
A::A() {
    cout << "Creating A\n";
    t = T(100);
    cout << "End\n";
}

void A::add(string name, string num) {
    cout << "calling add in A\n";
    t.add(name, num);
}
 
 T.hpp 
 
class T {
    private:
        E * t;
    public:
        T(int size=100);
        ~T();
    void add(std::string name, std::string num);
 
 T.cpp 
 
T::T(int size) : size(size) {
    t = new E[size];
}

T::~T() {
    cout << "Destroying\n";
    // delete[] t; // if I don't comment this I get Segfault when calling add method
}


void T::add(string name, string num){
        E e = E(name, num);
        t[0] = e;
}
 
 main.cpp中 
 
 int main(int argc, char* argv[]) {
    A a;
    a.add("name", "num");
}
 
 产量 
 
Creating A
Destroying
End
calling add in A
Destroying

In my constructor I initialize a field. The field is destroyed just after the initialization. Here's my code and my test:
 
A.hpp
 
class A {
    private:
        T t;

    public:
    A(); 
    ~A();

    void add(string name, string num);
}; 
 
A.cpp
 
A::A() {
    cout << "Creating A\n";
    t = T(100);
    cout << "End\n";
}

void A::add(string name, string num) {
    cout << "calling add in A\n";
    t.add(name, num);
}
 
T.hpp
 
class T {
    private:
        E * t;
    public:
        T(int size=100);
        ~T();
    void add(std::string name, std::string num);
 
T.cpp
 
T::T(int size) : size(size) {
    t = new E[size];
}

T::~T() {
    cout << "Destroying\n";
    // delete[] t; // if I don't comment this I get Segfault when calling add method
}


void T::add(string name, string num){
        E e = E(name, num);
        t[0] = e;
}
 
main.cpp
 
 int main(int argc, char* argv[]) {
    A a;
    a.add("name", "num");
}
 
Output
 
Creating A
Destroying
End
calling add in A
Destroying

原文：