创建一个没有默认构造函数的类的智能指针数组

Question

I'm referring to the question , Can we create an array of std::unique_ptr to a class which has deleted default constructor as below, How to pass the string argument.

#include <iostream>  
#include <string>  
#include <memory>

using namespace std;

class A 
{
    string str;
public:
    A() = delete;
    A(string _str): str(_str) {}
    string getStr() 
    {
        return str;
    }
};

int main()
{
    unique_ptr<A[]> ptr = make_unique<A[]>(3);
    unique_ptr<A[]> arr[3] = make_unique<A[]>(3);
    // Do something here
    return 0;
}

Answer 1

For an array of smart pointers:

unique_ptr<A> ptr[3];

for (auto& p : ptr)
    p = make_unique<A>("hello");

Answer 2

You can't do that with make_unique . But you can use this:

unique_ptr<A[]> ptr(new A[3]{{"A"}, {"B"}, {"C"}});

Before C++11 - it was very hard (that can be done with placement new etc).