iOS 中 flags 结构的用途是什么？答案

【问题标题】：What is the purpose of the flags struct in iOS?iOS 中 flags 结构的用途是什么？
【发布时间】：2011-12-16 04:43:04
【问题描述】：

struct
{
    unsigned resizesCellWidths:1;
    unsigned numColumns:6;
    unsigned separatorStyle:3;
    unsigned allowsSelection:1;
    unsigned backgroundViewExtendsUp:1;
    unsigned backgroundViewExtendsDown:1;
    unsigned usesPagedHorizontalScrolling:1;
    unsigned updating:1;
    unsigned ignoreTouchSelect:1;
    unsigned needsReload:1;
    unsigned allCellsNeedLayout:1;
    unsigned isRotating:1;
    unsigned clipsContentWidthToBounds:1;
    unsigned isAnimatingUpdates:1;
    unsigned requiresSelection:1;
    unsigned contentSizeFillsBounds:1;
    unsigned delegateWillDisplayCell:1;
    unsigned delegateWillSelectItem:1;
    unsigned delegateWillSelectItemMultiTouch:1;
    unsigned delegateWillDeselectItem:1;
    unsigned delegateDidSelectItem:1;
    unsigned delegateDidSelectItemMultiTouch:1;
    unsigned delegateDidDeselectItem:1;
    unsigned delegateGestureRecognizerActivated:1;
    unsigned delegateAdjustGridCellFrame:1;
    unsigned delegateDidEndUpdateAnimation:1;
    unsigned dataSourceGridCellSize:1;
    unsigned int isEditing:1;
    unsigned __RESERVED__:1;
} _flags;

这个结构的用途是什么？
每行末尾的 :1 表示法是什么意思？
没有显式类型时unsigned修饰符是什么意思？

谢谢

【问题讨论】：

unsigned 暗示为unsigned int，除非另有说明。

标签： c ios struct bitflags

【解决方案1】：

那些是bitfields。由于其中大部分是标志，它们只有 2 个可能的值，因此无需为每个字段分配超过 1 位。（该结构中有几个例外）

unsigned 可以单独作为一个类型。这只是一个unsigned int。

【讨论】：