C++ 对象在从函数返回时被销毁
我正在从事qt项目，并注意到我的应用程序崩溃。C++ 对象在从函数返回时被销毁,c++,qt,constructor,namespaces,C++,Qt,Constructor,Namespaces,我正在从事qt项目，并注意到我的应用程序崩溃。 调试时，我发现这是因为没有创建/初始化qpushbutton对象 现在我不明白为什么它没有被初始化 我在名称空间中编写了一个函数，它为所有Qpushbutton调用构造函数，我通过引用将对象传递给该函数 那么，一旦函数返回，它不应该保留它的值吗？但在我的例子中，函数一返回就被销毁了？ 它与名称空间有关吗 任何帮助或批评都会有帮助吗 MY_Utility.h class MY_Utility { private: QPushB
调试时，我发现这是因为没有创建/初始化qpushbutton对象 现在我不明白为什么它没有被初始化 我在名称空间中编写了一个函数，它为所有Qpushbutton调用构造函数，我通过引用将对象传递给该函数 那么，一旦函数返回，它不应该保留它的值吗？但在我的例子中，函数一返回就被销毁了？ 它与名称空间有关吗 任何帮助或批评都会有帮助吗
MY_Utility.h
class MY_Utility
{
private:
QPushButton* add_cal_button_;
QPushButton* sub_cal_button_;
QPushButton* mul_button_;
}
My_Utility.cpp
namespace
{
void create_push_button_for_cal( QPushButton *button_cal, QString button_name, QGridLayout *grid, int grid_row, int grid_col )
{
button_cal = new QPushButton( button_name );
if(!button_cal )
{
msg.setInformativeText("The code does not come here so object is created");
QMessageBox msg;
msg.setText("Messsage");
msg.setInformativeText("OBject not initialised in create_push button ");
msg.exec();;
}
button_cal->setFixedSize( 200 , 40 );
button_cal->setVisible( false );
grid->addWidget( button_cal, grid_row, grid_col );
}
// function where we call all button created
void create_main_view( MY_Utility* main_p, QTreeWidget* tree_p, QTableWidget* table_p, QPushButton* add_cal_button_,
QPushButton* sub_cal_cal_button_,
QPushButton* mul_cal_button_,
{
QWidget* center_p = new QWidget( main_p );
QHBoxLayout* layout_p = new QHBoxLayout( center_p );
QGridLayout* grid = new QGridLayout( center_p );
grid->setSpacing( 1 );
create_push_button_for_cal( add_cal_button_, "addition_calculate" , grid, 1, 2 );
if( !add_cal_button_ )
{
QMessageBox msg;
msg.setText("Messsage");
msg.setInformativeText("OBject not initialised in first part of message why not ?? ");
msg.exec();;
}
create_push_button_for_cal( sub_cal_cal_button_ ,"sub_Calculate", grid, 2, 2 );
create_push_button_for_cal( mul_cal_button_ , "multplication_Calculate", grid, 3, 2 );
// Make the QWidget the central widget so we can resize within it
main_p->setCentralWidget( center_p );
bla ..
bla ..
}
}
My_Utility::set_all_cal_button_visible(){
add_cal_button_->setVisible(true) ; // it crashes here
}
<>你的问题是C++问题，不是QT问题。
void create_push_button_for_cal(QPushButton *button_cal, QString button_name)
{
button_cal = new QPushButton(button_name);
Q_ASSERT(button_cal);
}
按钮\u calnewnewnewnewQPushButton * create_push_button_for_cal(const QString & button_name) {
QScopedPointer<QPushButton> btn(new QPushButton(button_name));
...
// If any code here throws an exception, the scoped pointer will delete
// the button instance, so that it won't leak.
...
return btn.take();
}
QPushButton*为校准创建按钮（常量字符串和按钮名称）{
QScopedPointer btn（新的QPushButton（按钮名称））；
...
//如果此处的任何代码引发异常，则作用域指针将删除
//按钮实例，这样它就不会泄漏。
...
返回btn.take（）；
}