Difference between smart pointer and raw pointer in c++

Diese kleine Demonstration zeigt den Unterschied, wie man die sogenannten Smartpointer in c++ benutzt. Die klugen Zeiger sorgen dafür, dass zuvor reservierter Speicher automatisch freigegeben wird, sobald diese Zeiger nicht mehr benötigt werden. Ein interner Zähler zählt die Anzahl der Referenzen. Wird der Wert 0 erreicht, so wird der Speicher freigegeben.

This small c++ application shows the difference between using smartpointer and raw pointer. Smartpointer frees memory automatically when this pointer is not needed anymore.

#include <iostream>
#include <memory>

/* raw pointer, the legacy way */
std::string* createRawPointer(const std::string &data){
    return new std::string(data);
}

void doSomethingWithRawPointer(std::string &raw){
    raw.append(" NEW DATA");
}

void deleteRawPointer(std::string *raw){
    delete raw;
}

/* smart pointer, the modern way to wrap a raw pointer */
std::unique_ptr<std::string> createSmartPointer(const std::string &data){
    return std::unique_ptr<std::string>(new std::string(data));
}

void doSomethingWithSmartPointer(std::unique_ptr<std::string> &smart){
    std::string *content = smart.get();
    content->append(" NEW DATA");
}

void deleteSmartPointer(std::unique_ptr<std::string> &smart){
    /* no action required to delete */
}

int main(){
    /* raw pointer example */
    std::string data = "Raw data";
    std::string *rawpointer = createRawPointer(data);
    std::cout << "before " << *rawpointer << '\n';
    doSomethingWithRawPointer(*rawpointer);
    std::cout << "after " << *rawpointer << '\n';
    deleteRawPointer(rawpointer);

    /* smart pointer example */
    data = "Smart data";
    std::unique_ptr<std::string> smart = createSmartPointer(data);
    std::cout << "before " << *smart.get() << '\n';
    doSomethingWithSmartPointer(smart);
    std::cout << "after " << *smart.get() << '\n';
    deleteSmartPointer(smart);
}