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/