C++ Smart Unique Pointer via make_unique<>()

Introduction

A better way to initialize a unique pointer is through an std::make_unique<some_type>(some_value) function, where we specify the type for the object in angle brackets and the value for the object pointer points at in parentheses: 

#include <iostream> 
#include <memory> 

int main() /*from   ww  w.  j a va2s . com*/
{ 
    std::unique_ptr<int> p = std::make_unique<int>(123); 
    std::cout << *p; 
}

The std::make_unique function was introduced in the C++14 standard.

Make sure to compile with the -std=c++14 flag to be able to use this function.

We can create a unique pointer that points to an object of a class and then use its -> operator to access object members: 

#include <iostream> 
#include <memory> 

class MyClass //  w  w  w  . j  av  a2s  .c  o m
{ 
public: 
    void printmessage() 
    { 
        std::cout << "Hello from a class."; 
    } 
}; 

int main() 
{ 
    std::unique_ptr<MyClass> p = std::make_unique<MyClass>(); 
    p->printmessage(); 
}

The object gets destroyed once p goes out of scope.

So, prefer a unique pointer to raw pointer and their new-delete mechanism.

Once p goes out of scope, the pointed-to object of a class gets destroyed.

We prefer this function to raw new operator when creating unique pointers: 

#include <iostream> 
#include <memory> 

class MyClass /*from  w  w w  .  j  av a 2  s  .  co  m*/
{ 
private: 
    int x; 
    double d; 
public: 
    MyClass(int xx, double dd) 
         : x{ xx }, d{ dd }    {} 
    void printdata() { std::cout << "x: " << x << ", d: " << d; } 
}; 

int main() 
{ 
    auto p = std::make_unique<MyClass>(123, 456.789); 
    p->printdata(); 
}



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