传递对 QPixmap ctor 的引用
当我尝试传递似乎是对我的 QPixmap 的引用时，我收到错误：
error: no matching function for call to ‘QGraphicsScene::addItem(QGraphicsPixmapItem (&)(QPixmap))’
问题是我不知道该引用来自哪里，尽管我猜测它来自来自迭代器。
void MainWindow::addItems(std::map<std::string, QString> * items)
{
std::map<std::string, QString>::const_iterator current;
for(current = items->begin(); current != items->end(); ++current)
{
QString cur = current->second;
QGraphicsPixmapItem item(QPixmap(cur));
_scene->addItem(item);
}
}
如果是这种情况，有没有办法取消引用迭代器？不然的话，我到底做错了什么？
调用它的代码
int main(int argc, char *argv[])
{
std::map<std::string, QString> * items;
items->insert(std::pair<std::string, QString>("ozone", ":/images/ozone_sprite.png"));
QApplication a(argc, argv);
MainWindow window;
window.addItems(items);
window.show();
delete items;
return a.exec();
}
When I try to pass what appears to be a reference to my QPixmap, I get an error:
error: no matching function for call to ‘QGraphicsScene::addItem(QGraphicsPixmapItem (&)(QPixmap))’
The problem is that I don't know where this reference is coming from, though I'm guessing it's coming from the iterator.
void MainWindow::addItems(std::map<std::string, QString> * items)
{
std::map<std::string, QString>::const_iterator current;
for(current = items->begin(); current != items->end(); ++current)
{
QString cur = current->second;
QGraphicsPixmapItem item(QPixmap(cur));
_scene->addItem(item);
}
}
If that's the case, is there a way to de-reference the iterator? Otherwise, what is it that I'm doing wrong?
The code which calls it
int main(int argc, char *argv[])
{
std::map<std::string, QString> * items;
items->insert(std::pair<std::string, QString>("ozone", ":/images/ozone_sprite.png"));
QApplication a(argc, argv);
MainWindow window;
window.addItems(items);
window.show();
delete items;
return a.exec();
}
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评论（1）
您已经犯了所谓的 C++ 的“最令人烦恼的解析”。具体来说，它：
声明一个名为
item的函数，该函数采用QPixmap类型的单个参数并返回一个QGraphicsPixmapItem。要解决此问题，请写入：请参阅此处：
http://en.wikipedia.org/wiki/Most_veshing_parse
就错误而言，请注意您正在尝试使用
QGraphicsPixmapItem (&)(QPixmap)类型的参数调用addItem- 也就是说，引用一个采用QPixmap并返回QGraphicsPixmapItem的函数（这是表达式item的类型）。You've fallen foul of what's known as C++'s 'most vexing parse'. Specifically, this:
declares a function called
itemthat takes a single parameter of typeQPixmapand returns aQGraphicsPixmapItem. To fix this, write:See here:
http://en.wikipedia.org/wiki/Most_vexing_parse
As far as the error goes, note that you're trying to call
addItemwith an argument of typeQGraphicsPixmapItem (&)(QPixmap)- that is, reference to a function taking aQPixmapand returning aQGraphicsPixmapItem(which is the type of the expressionitem).