在 Qt 中如何将单例实例连接到插槽？
我在 Qt Creator 中编程并遇到了问题。我创建了一个单例类，我试图将它连接到小部件中的一个插槽，但它不接受返回的指针 来自 Singleton::getInstance() 作为发出信号的同一实例。
我的代码如下：
class Widget : public QWidget
{
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
~Widget();
private slots:
void setString(int var);
}
实现：
connect(Singleton::getInstance(),SIGNAL(changeString(int)),this,SLOT(setString(int)));
单例类中的信号：
signals:
void changeString(int var);
单例类中对信号的调用：
emit(Singleton::getInstance()->changeString(5));
信号发出时没有任何反应。调试器不进入插槽。
I'm programming in Qt Creator and encountered a problem. I made a singleton class, and I'm trying to connect it to a slot in the widget, but it doesn't take the pointer that returns
from Singleton::getInstance() as the same instance that emits the signal.
My code is as follows:
class Widget : public QWidget
{
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
~Widget();
private slots:
void setString(int var);
}
Implementation:
connect(Singleton::getInstance(),SIGNAL(changeString(int)),this,SLOT(setString(int)));
Signal in the singleton class:
signals:
void changeString(int var);
the call to the signal in the singleton class:
emit(Singleton::getInstance()->changeString(5));
Nothing happens when signal emits. The debugger doesn't enter the slot.
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评论（4）
最有可能的是插槽的方法签名不同 -
setString(IMSS_Status);与setString(int);另外，如果是自定义类型，您应该调用
使用元类型系统正确注册它。否则，例如，排队的槽执行将无法工作。
Most probably it's the differing method signature of the slot -
setString(IMSS_Status);vs.setString(int);Also, in case of a custom type, you should call
to register it correctly with the meta type system. Otherwise, queued slot executions won't work, for instance.
您的问题可能是由方法签名引起的。在与插槽建立连接信号之前，您应该使用
qRegisterMetaType("Class Definition name"); 定义到系统的信号， 并且是changeString签名的信号吗？ “void changeString(int)”
我遇到了你的问题，我通过制作 qRegisterMetaType 和控制签名解决了我的问题。
Your problem may be caused by signature of the methods. Before you make connect signal with slot u should define your signal to system by using
qRegisterMetaType<Your Class >("Class Definition name");And is the signal of changeString signature ? "void changeString(int)"
i had encountered your problem and i solved my problem by making qRegisterMetaType and controlling signatures.
Singleton 类也有 Q_OBJECT 宏吗？我不知道它是否也需要它。
Does the Singleton class have the
Q_OBJECTmacro also? I don't know if it needs it also or not.我倾向于
emit(Singleton::getInstance()->changeString(5));不正确。emit 应该从
Singleton函数内部调用，如下所示：emit(changeString(5));我很惊讶您发布的代码在没有警告的情况下编译和运行，我会预计会出现有关信号不存在的运行时错误。
I would lean towards
emit(Singleton::getInstance()->changeString(5));not being correct.emit should be called from inside a
Singletonfunction as follows:emit(changeString(5));I'm surprised the code you posted compiles and runs without warning, I would have expected a runtime error about the signal not existing.