NS_OPTIONS匹配

Question

我正在尝试实现以下typedef

typedef NS_OPTIONS (NSInteger, MyCellCorners) {
    MyCellCornerTopLeft,
    MyCellCornerTopRight,
    MyCellCornerBottomLeft,
    MyCellCornerBottomRight,
};

并正确分配值

MyCellCorners cellCorners = (MyCellCornerTopLeft | MyCellCornerTopRight);

在绘制我的单元格时,如何检查哪些选项匹配,以便我可以正确绘制它.

Answer 1

使用位掩码:

typedef NS_OPTIONS (NSInteger, MyCellCorners) {
    MyCellCornerTopLeft = 1 << 0,
    MyCellCornerTopRight = 1 << 1,
    MyCellCornerBottomLeft = 1 << 2,
    MyCellCornerBottomRight = 1 << 3,
};

MyCellCorners cellCorners = MyCellCornerTopLeft | MyCellCornerTopRight;

if (cellCorners & MyCellCornerTopLeft) {
    // top left corner set
}

if (etc...) {

}

Answer 2

检查此值的正确方法是首先按位AND值,然后检查是否与所需值相等.

MyCellCorners cellCorners = MyCellCornerTopLeft | MyCellCornerTopRight;

if ((cellCorners & MyCellCornerTopLeft) == MyCellCornerTopLeft) {
    // top left corner set
}

以下参考资料解释了为什么这是正确的,并提供了枚举类型的其他见解.

参考:检查位值掩码中的值