[英]What is the purpose of the flags struct in iOS?
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
notation at the end of each line signify? :1
表示什么? unsigned
modifier when there is no explicit type? unsigned
修饰符是什么意思? Thanks 谢谢
Those are bitfields . 那些是位域 。 Since most of these are flags, they only have 2 possible values, so there's no need to assign more than 1 bit to each field.
由于大多数都是标志,因此它们只有2个可能的值,因此无需为每个字段分配超过1位的值。 (with a couple exceptions in that struct)
(该结构中有几个例外)
unsigned
can stand alone as a type. unsigned
可以单独作为一种类型。 It's just an unsigned int
. 这只是一个
unsigned int
。
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