constref.cpp

来自「压缩包里有教材<<C++模式设计-基于QT4开源跨平台开发框架&gt」· C++ 代码 · 共 35 行

class Person {

public:
    void setNameV( QString newName) {
        newName += " Smith";  /* Changes a temporary that's
            about to be destroyed. */
        m_Name = newName;
    }

    void setNameCR( const QString& newName) {
//      newName += " Python"; /* Error: can't change const&. */
        m_Name = newName;
    }
    void setNameR( QString& newName) {
        newName += " Dobbs"; /* changes the original QString */
        m_Name = newName;
    }
private:
    QString m_Name;
};

int main() {
    Person p;
    QString name("Bob");
    p.setNameCR(name);  /* No temporaries are created. */ 
//  p.setNameR("Monty");  /* Error: cannot convert to a QString&. */
    p.setNameCR("Monty");  /* char* converts to temporary
        and gets passed by const reference. */
    p.setNameV("Connie");  /* Temporary QString #1 is created to
        convert char* to QString. Temporary #2 is created when it is
        passed by value. */
    p.setNameR(name);      /* No temporaries are created. */
    cout << name;         
}