在Cocoa和Cocoa Touch框架中,枚举用作常量.我知道如何使用它,除了在一种情况下,这种情况下你可以通过|
操作符作为参数传递多个值.比如:
pageControl.autoresizingMask = (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin);
enum声明如下:
enum {
UIViewAutoresizingNone = 0,
UIViewAutoresizingFlexibleLeftMargin = 1 << 0,
UIViewAutoresizingFlexibleWidth = 1 << 1,
UIViewAutoresizingFlexibleRightMargin = 1 << 2,
UIViewAutoresizingFlexibleTopMargin = 1 << 3,
UIViewAutoresizingFlexibleHeight = 1 << 4,
UIViewAutoresizingFlexibleBottomMargin = 1 << 5
};
typedef NSUInteger UIViewAutoresizing;
如何定义这种类型的枚举(即<<
的含义),以及如何在作为参数传递时判断多个值?