目标:我必须将一个对象复制到另一个对象中。

我想到了不使用赋值或复制构造器来复制它,但是它不会编译。所以我有使用复制构造器/赋值运算符。

问题

现在我有两个问题?

1)我真的需要复制构造函数和赋值运算符吗?据我所知,我没有在成员变量中使用任何指针,所以没有必要使用复制构造函数吗?

但是我的对象是一个指针,所以我可能需要它吗?

2)如果我的以下代码正确,为什么我会收到以下所示的错误
无法从'const Home_instance *'转换为'Home_instance *'

home_data.h

struct home_data
{
    QString                           area_address_;
    QVector<QString>                   home_numbers_;
    QMap< QString, QList<QByteArray> > area_to_home_mapping;
};


Home_instance.h

class Home_instance : public QObject
{
    Q_OBJECT

public:
    Home_instance( const Home_data& data, QObject* parent_p = 0 );
    Home_instance();
    Home_instance( const Home_instance& rhs );
    Home_instance& operator=( const Home_instance& rhs );
    ~Home_instance();
// some otehr functions

private:
    Home_data data_;


}

Home_instance.cpp

//constructors

Firmware_instance::Home_instance( )
{
}

Home_instance::Home_instance( const Home_data& data, QObject* parent_p )
: QObject( parent_p ),
  data_  ( data )
{}

Home_instance::Home_instance( const Home_instance& rhs )
{
    data_.ip_address_            = rhs.data_.ip_address_;
    data_.serial_numbers_        = rhs.data_.serial_numbers_;
    data_.serial_to_slot_mapping = rhs.data_.serial_to_slot_mapping;

}

 Home_instance& Home_instance::operator=( const Home_instance& rhs )
 {
    data_.ip_address_            = rhs.data_.ip_address_;
    data_.serial_numbers_        = rhs.data_.serial_numbers_;
    data_.serial_to_slot_mapping = rhs.data_.serial_to_slot_mapping;
    return *this;
 }

Home_instance::~Home_instance()
{
   // do we actually need destructor ?
}

//  in some other Dialog window say Council.h &cpp


class Council
{

// some other variable decl
private:
Home_instance*            Home_instance_p_;
Home_data                 Home_data_p_;

}


in council.cpp

// in constructor

{


connect( udp_p_,    SIGNAL( discovered_Home( const Home_instance* ) ), this, SLOT( new_Home( const Home_instance* ) ) );
}


// in function new_home

void Council::new_home( const Home_instance* Home_old_instance )

{

// bla bla

Home_instance_p_  =     Home_old_instance; // error can not convert from 'const Home_instance *' to 'Home_instance *'
}

谢谢

最佳答案

这个

Home_instance_p_  =     Home_old_instance;

不复制对象,而是尝试复制指针。

你要
Home_instance_p_ = new Home_instance(*Home_old_instance);

然后在delete Home_instance_p_中添加~Council

关于c++ - 我需要复制构造函数吗?以及如何使用复制构造函数将const对象复制到非const对象,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/21284896/

10-12 14:55
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