C2665：'QObject::connect‘：3种重载都不能转换所有参数类型
C2665：'QObject::connect‘：3种重载都不能转换所有参数类型
提问于 2015-07-16 21:26:07
我主要有以下代码
QProcess process;
QObject::connect(&process, &QProcess::error, [](QProcess::ProcessError error)
{
qDebug() << error;
}, Qt::QueuedConnection);
bool launched = process.startDetached("D:\temp.exe");它在编译时生成此错误。
D:\main.cpp:5: error: C2665: 'QObject::connect' : none of the 3 overloads could convert all the argument types c:\qt\5.3\msvc2013_64\include\qtcore\qobject.h(205): could be
'QMetaObject::Connection QObject::connect(const QObject *,const char
*,const char *,Qt::ConnectionType) const' c:\qt\5.3\msvc2013_64\include\qtcore\qobject.h(201): or
'QMetaObject::Connection QObject::connect(const QObject *,const QMetaMethod &,const QObject *,const QMetaMethod &,Qt::ConnectionType)' c:\qt\5.3\msvc2013_64\include\qtcore\qobject.h(198): or
'QMetaObject::Connection QObject::connect(const QObject *,const char
*,const QObject *,const char *,Qt::ConnectionType)' while trying to match the argument list '(QProcess *, overloaded-function, RunGUIMode::<lambda_5d6e7ee926a623cea2a0e4469253d55f>, Qt::ConnectionType)'有人能帮帮我，告诉我我做错了什么吗？
我想从QProcess类连接一个信号到我的lambda
回答 1
Stack Overflow用户
发布于 2015-07-17 05:33:38
我不应该发布这个答案，但老实说，这不是same question，它更复杂。
首先，为什么第一个版本不能工作。因为如果不提供receiver，就不能使用附加参数(连接类型)。这意味着下一个是错误的。
connect(&process, static_cast<void (QProcess::*)(QProcess::ProcessError)>
(&QProcess::error),[=](QProcess::ProcessError pError) {
qWarning() << "error " << pError;
},Qt::QueuedConnection);但下一步是正确的：
connect(&process, static_cast<void (QProcess::*)(QProcess::ProcessError)>
(&QProcess::error), this , [=](QProcess::ProcessError pError) {
qWarning() << "error " << pError;
},Qt::QueuedConnection);如果你想知道为什么，请看qobject.h。我在这个文件中做了一些修改，只是为了更准确(不要更改这个文件！)
//first
//connect to a functor
template <typename Func1, typename Func2>
static inline typename QtPrivate::QEnableIf<QtPrivate::FunctionPointer<Func2>::ArgumentCount == -1, QMetaObject::Connection>::Type
connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
{
qDebug("There is no here argument for connection, isn't it?");
return connect(sender, signal, sender, slot, Qt::DirectConnection);
}
//second
//connect to a functor, with a "context" object defining in which event loop is going to be executed
template <typename Func1, typename Func2>
static inline typename QtPrivate::QEnableIf<QtPrivate::FunctionPointer<Func2>::ArgumentCount == -1, QMetaObject::Connection>::Type
connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, const QObject *context, Func2 slot,
Qt::ConnectionType type = Qt::AutoConnection)
{
qDebug("This will be called, and as you can see you need specify the context if you want to use connection type.");
//...其次，当您运行此代码时，您将得到：
连接:不能将类型为'QProcess::ProcessError‘的参数排队(确保'QProcess::ProcessError’使用qRegisterMetaType()注册。)
因此，您需要在连接之前添加qRegisterMetaType<QProcess::ProcessError>("QProcess::ProcessError");。
因此，最终版本是：
qRegisterMetaType<QProcess::ProcessError>("QProcess::ProcessError");
QProcess process;
connect(&process, static_cast<void (QProcess::*)(QProcess::ProcessError)>
(&QProcess::error), this , [=](QProcess::ProcessError pError) {
qWarning() << "error " << pError;
},Qt::QueuedConnection);
process.start("MyProgram");
bool launched = process.startDetached("example");页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/31464822
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