我一直试图理解如何将其作为const引用传递.
我有以下课程:
class DBContext : public QObject
在我的班级MainWindow中,我将其定义为folows:
private:
QScopedPointer<DBContext> dbContext;
如何定义存储类:
class StorageData : public QObject
{
Q_OBJECT
public:
StorageData(QObject *parent = 0);
~StorageData();
void SetDBContext(const QScopedPointer<DBContext> &db_context);
private:
QScopedPointer<DBContext> dbContext;
在StorageData SetDBContext()中,我尝试使用以下内容进行分配:
void StorageData::SetDBContext(const QScopedPointer<DBContext> &db_context)
{
dbContext = db_context;
}
然后在MainWindow构造函数中初始化它:
dbContext.reset(new DBContext(this));
StorageData storage;
storage.SetDBContext(dbContext);
在StorageData函数SetDBContext()中使用以下内容:
_DBContext = db_context;
我收到一个错误:
‘QScopedPointer> :: operator =’:无法访问类’QScopedPointer>’中声明的私有成员
更新
采用QSharedPointer和QWeakPointer的提示.这是使用这两个指针的有效方法吗?我也在A类和A类上正确使用clear() B’
class A
private:
QWeakPointer<DBContext> dbContext;
void A::~A()
{
dbContext.clear()
}
void A::SetDBContext(QWeakPointer<DBContext> db_context)
{
dbContext= db_context;
}
void A::UseCode()
{
QSharedPointer<DBContext> ptrContext= dbContext.toStrongRef();
..
}
class B constructor:
private:
QSharedPointer<DBContext> dbContext;
在构造函数中:
B::B()
{
dbContext.reset(new DBContext(this));
QWeakPointer<DBContext> ptrDBConnect = dbContext;
storage.SetDBContext(ptrDBConnect);
}
在析构函数中:
B::~B()
{
dbContext.clear();
}
最佳答案 从QScopedPointer的文档:
QScopedPointer intentionally has no copy constructor or assignment
operator, such that ownership and lifetime is clearly communicated.
QScopedPointer的目的是使您指向的对象的生命周期与QScopedPointer的范围保持一致.如果你可以分配/复制它,那么它就会失败.