[英]How to create a QSharedPointer<QMap<a,b>> with an initializer list?
在 Qt 5.12.4 中,我嘗試動態創建QSharedPointer<QMap<int,bool>>
。 我知道我能做到
QMap<int, bool> mp = { { 1, true } };
以及動態地
QMap<int, bool>* mpptr = new QMap<int, bool> { { 1, false } };
我知道我可以像這樣創建我的QSharedPointer
:
QMap<int, bool>* mpptr = new QMap<int, bool> { { 1, false } };
QSharedPointer<QMap<int, bool>> shraredmpptr(mpptr);
我想一口氣做到這一點,但我無法完成。 我試過最明顯的
QSharedPointer<QMap<int, bool>> mpsptr =
QSharedPointer<QMap<int, bool>>::create(new QMap<int, bool> { { 1, false } });
但無濟於事。 編譯器警告我我的類型不匹配,但我沒有看到我必須更改代碼才能編譯的地方。 有任何想法嗎? 提前致謝。
In file included from D:\Qt\5.12.4\mingw73_64\include/QtCore/qsharedpointer.h:48:0,
from D:\Qt\5.12.4\mingw73_64\include/QtCore/qdebug.h:54,
from D:\Qt\5.12.4\mingw73_64\include\QtCore/qloggingcategory.h:44,
from D:\Qt\5.12.4\mingw73_64\include\QtCore/QLoggingCategory:1,
from ..\..\..\..\myLibsQt\src\libs/a/foo.h:4,
from ..\..\..\..\myLibsQt\src\libs/a/bar.h:8,
from ..\..\..\..\myLibsQt\src\libs/b/baz.h:8,
from ..\..\..\..\myLibsQt\src\libs/c/bla.h:8,
from ..\..\..\..\myLibsQt\src\libs\c\blubb.cpp:1:
D:\Qt\5.12.4\mingw73_64\include/QtCore/qsharedpointer_impl.h: In instantiation of 'static QSharedPointer<T> QSharedPointer<T>::create(Args&& ...) [with Args = {QMap<int, bool>*}; T = QMap<int, bool>]':
..\..\..\..\myLibsQt\src\libs\c\blubb.cpp:27:80: required from here
D:\Qt\5.12.4\mingw73_64\include/QtCore/qsharedpointer_impl.h:445:9: error: no matching function for call to 'QMap<int, bool>::QMap(QMap<int, bool>*)'
new (ptr) T(std::forward<Args>(arguments)...);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from D:\Qt\5.12.4\mingw73_64\include/QtCore/qdebug.h:47:0,
from D:\Qt\5.12.4\mingw73_64\include\QtCore/qloggingcategory.h:44,
from D:\Qt\5.12.4\mingw73_64\include\QtCore/QLoggingCategory:1,
from ..\..\..\..\myLibsQt\src\libs/a/foo.h:4,
from ..\..\..\..\myLibsQt\src\libs/a/bar.h:8,
from ..\..\..\..\myLibsQt\src\libs/b/baz.h:8,
from ..\..\..\..\myLibsQt\src\libs/c/bla.h:8,
from ..\..\..\..\myLibsQt\src\libs\c\blubb.cpp:1:
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:1164:22: note: candidate: QMap<K, V>::QMap(const std::map<Key, T>&) [with Key = int; T = bool]
Q_OUTOFLINE_TEMPLATE QMap<Key, T>::QMap(const std::map<Key, T> &other)
^~~~~~~~~~~~
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:1164:22: note: no known conversion for argument 1 from 'QMap<int, bool>*' to 'const std::map<int, bool, std::less<int>, std::allocator<std::pair<const int, bool> > >&'
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:343:12: note: candidate: QMap<K, V>::QMap(QMap<K, V>&&) [with Key = int; T = bool]
inline QMap(QMap<Key, T> &&other) Q_DECL_NOTHROW
^~~~
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:343:12: note: no known conversion for argument 1 from 'QMap<int, bool>*' to 'QMap<int, bool>&&'
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:622:8: note: candidate: QMap<K, V>::QMap(const QMap<K, V>&) [with Key = int; T = bool]
inline QMap<Key, T>::QMap(const QMap<Key, T> &other)
^~~~~~~~~~~~
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:622:8: note: no known conversion for argument 1 from 'QMap<int, bool>*' to 'const QMap<int, bool>&'
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:330:12: note: candidate: QMap<K, V>::QMap(std::initializer_list<std::pair<_T1, _T2> >) [with Key = int; T = bool]
inline QMap(std::initializer_list<std::pair<Key,T> > list)
^~~~
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:330:12: note: no known conversion for argument 1 from 'QMap<int, bool>*' to 'std::initializer_list<std::pair<int, bool> >'
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:328:12: note: candidate: QMap<K, V>::QMap() [with Key = int; T = bool]
inline QMap() Q_DECL_NOTHROW : d(static_cast<QMapData<Key, T> *>(const_cast<QMapDataBase *>(&QMapDataBase::shared_null))) { }
^~~~
D:\Qt\5.12.4\mingw73_64\include/QtCore/qmap.h:328:12: note: candidate expects 0 arguments, 1 provided
mingw32-make[1]: *** [Makefile.Debug:1488: debug/blubb.o] Error 1
傳遞給創建的 arguments 直接傳遞給構造函數。 因此,您可以這樣做:
QSharedPointer<QMap<int, bool>> mpsptr = QSharedPointer<QMap<int, bool>>::create({
{ 1, false }
});
如果您使用 C++11 或更高版本,為什么不使用 auto?
auto mpsptr = QSharedPointer<QMap<int, bool>>::create({
{ 1, false }
});
這對我有用(用GCC, C++ x86 64bit編譯):
QSharedPointer<QMap<int, bool>> mpsptr = QSharedPointer<QMap<int, bool>>::create(QMap<int, bool>{{1, false}});
好的,我找到了一個適合我的答案。 上面的沒有用 msvc17 和我的 arm 工具鏈編譯。 我的第一種方法也會產生 memory 泄漏。
正確的做法是
QSharedPointer<QMap<int, bool>> mpsptr(new QMap<int, bool> { { 1, false } });
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