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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;
  1. 这个结构的目的是什么？
  2. :1每行末尾的符号是什么意思？
  3. unsigned没有显式类型时修饰符的含义是什么？

谢谢

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1 回答 1

5

这些是位域。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可以单独作为一种类型。这只是一个unsigned int.

于 2011-10-27T02:11:58.807 回答