問題描述
根據文檔，插槽的返回值沒有任何意義.
然而在生成的 moc 代碼中，我看到如果一個插槽返回一個值，這個值用于某些東西.知道它有什么作用嗎?
According to the documentation the return value from a slot doesn't mean anything.
Yet in the generated moc code I see that if a slot returns a value this value is used for something. Any idea what does it do?
這是我所談論的一個例子.這是取自 moc 生成的代碼.'message' 是一個不返回任何內容的槽，'selectPart' 被聲明為返回 int.
Here's an example of what I'm talking about. this is taken from code generated by moc. 'message' is a slot that doesn't return anything and 'selectPart' is declared as returning int.
case 7: message((*reinterpret_cast< const QString(*)>(_a[1])),(*reinterpret_cast< int(*)>(_a[2]))); break;
case 8: { int _r = selectPart((*reinterpret_cast< AppObject*(*)>(_a[1])),(*reinterpret_cast< int(*)>(_a[2])));
if (_a[0]) *reinterpret_cast< int*>(_a[0]) = _r; } break;
推薦答案
返回值僅在您想將插槽作為普通成員函數調用時才有用:
The return value is only useful if you want to call the slot as a normal member function:
class MyClass : public QObject {
Q_OBJECT
public:
MyClass(QObject* parent);
void Something();
public Q_SLOTS:
int Other();
};void MyClass::Something() {int res = this->Other();...}
void MyClass::Something() { int res = this->Other(); ... }
似乎這不是可以使用返回值的唯一方法，QMetaObject::invokeMethod 方法可用于調用插槽并獲取返回值.雖然看起來做起來有點復雜.
It seems that's not the only way the return value can be used, the QMetaObject::invokeMethod method can be used to call a slot and get a return value. Although it seems like it's a bit more complicated to do.
這篇關于Qt:插槽返回值的含義?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！