连接lambda时如何将Qt :: ConnectionType传递给QObject :: connect？

Question

我将lambdas连接到QObject信号:

    QObject::connect(handle, &BatchHandle::progressMax, [this](const ProcessHandle* const self, const int value) {
        this->maxProgress(value);
    });

上面的代码编译没有问题.

然而,Qt::QueuedConnection因为handle对象最终将移动到另一个线程,所以绝对必要.

我把它添加到我的代码中:

    QObject::connect(handle, &BatchHandle::finished, [this](const ProcessHandle* const self) {
        this->processIsRunning(false);
    }, (Qt::ConnectionType)Qt::QueuedConnection);

请注意我是如何添加显式强制转换以确保它正确标识值类型的.结果:

1>src\TechAdminServices\database\techCore\processes\import\ImportManagerDialog.cpp(191): error C2664: 'QMetaObject::Connection QObject::connect<void(__cdecl taservices::ProcessHandle::* )(const taservices::ProcessHandle *),Qt::ConnectionType>(const taservices::ProcessHandle *,Func1,const QObject *,Func2,Qt::ConnectionType)' : cannot convert parameter 3 from 'taservices::`anonymous-namespace'::<lambda58>' to 'const QObject *'
1>          with
1>          [
1>              Func1=void (__cdecl taservices::ProcessHandle::* )(const taservices::ProcessHandle *),
1>              Func2=Qt::ConnectionType
1>          ]
1>          No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

连接lambda时如何获得排队连接？

Answer 1

我认为你需要使用QObject::connect重载,它允许你指定应该调用lambda的上下文...

QObject::connect(
  handle,
  &BatchHandle::progressMax,
  target_context,   /* Target context parameter. */
  [this](const ProcessHandle* const self, const int value)
  {
    this->maxProgress(value);
  },
  Qt::QueuedConnection);