Question

C++ Qt中setBrush我只发现了一种实现方式，为何以下语句中有两种？

painter.setBrush(QBrush(Qt::blue,Qt::Dense3Pattern))

painter.setBrush(Qt::blue)

Qt帮助文档是这样的：

void QPainter::setBrush(const QBrush &brush)
Sets the painter's brush to the given brush.
The painter's brush defines how shapes are filled.
See also brush() and Settings.
void QPainter::setBrush(Qt::BrushStyle style)
This is an overloaded function.
Sets the painter's brush to black color and the specified style.

Answer 1

很明显第一种是显示构造一个QBrush对象，后者是隐式转换成一个QBrush了，你可以看看QBrush的构造函数有哪几种。

Answer 2

这不是两个重载函数吗

Answer 3

多态，用参数类型决定调用哪一个，功能不同！