cocoa - 创建行时，NSTableView 的委托(delegate)接收 awakeFromNib 消息

Question

在我的项目中，有一个 xib 文件，其文件所有者设置为 NSViewController 的子类。这个xib文件有一个NSView，里面有一个基于 View 的NSTableView。 NSViewController 子类实现了协议(protocol)NSTableViewDelegate，并且在 IB 中，NSTableView 的委托(delegate)连接到文件的所有者。当通过绑定(bind)创建 View 时，将使用以下调用堆栈调用 viewController 的 awakeFromNib 方法:

#0  0x000000010000584b in -[TheViewController awakeFromNib] 
#1  0x00007fff890f9bd8 in -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] ()
#2  0x00007fff893101d6 in -[NSNib _instantiateNibWithExternalNameTable:] ()
#3  0x00007fff89310c7a in -[NSNib instantiateNibWithExternalNameTable:] ()
#4  0x00007fff892bcac4 in -[NSTableRowData _unarchiveViewWithIdentifier:owner:] ()
#5  0x00007fff892be57b in -[NSTableView(NSTableViewViewBased) makeViewForTableColumn:row:] ()
#6  0x00007fff892be1b2 in -[NSTableRowData _addViewToRowView:atColumn:row:] ()
#7  0x00007fff892bde7f in -[NSTableRowData _addViewsToRowView:atRow:] ()
#8  0x00007fff892bc415 in -[NSTableRowData _addRowViewForVisibleRow:withPriorView:] ()
#9  0x00007fff892bc19a in -[NSTableRowData _addRowViewForVisibleRow:withPriorRowIndex:inDictionary:withRowAnimation:] ()
#10 0x00007fff892bb469 in -[NSTableRowData _unsafeUpdateVisibleRowEntries] ()
#11 0x00007fff892bb001 in -[NSTableRowData updateVisibleRowViews] ()
#12 0x00007fff892930fb in -[NSTableView viewWillDraw] ()
#13 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#14 0x00007fff884d50b6 in __NSArrayEnumerate ()
#15 0x00007fff8917092d in -[NSView viewWillDraw] ()
#16 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#17 0x00007fff884d50b6 in __NSArrayEnumerate ()
#18 0x00007fff8917092d in -[NSView viewWillDraw] ()
#19 0x00007fff891fb455 in -[NSScrollView viewWillDraw] ()
#20 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#21 0x00007fff884d50b6 in __NSArrayEnumerate ()
#22 0x00007fff8917092d in -[NSView viewWillDraw] ()
#23 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#24 0x00007fff884d50b6 in __NSArrayEnumerate ()
#25 0x00007fff8917092d in -[NSView viewWillDraw] ()
#26 0x00007fff89247e0d in -[NSBox viewWillDraw] ()
#27 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#28 0x00007fff884d50b6 in __NSArrayEnumerate ()
#29 0x00007fff8917092d in -[NSView viewWillDraw] ()
#30 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#31 0x00007fff884d50b6 in __NSArrayEnumerate ()
#32 0x00007fff8917092d in -[NSView viewWillDraw] ()
#33 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#34 0x00007fff884d50b6 in __NSArrayEnumerate ()
#35 0x00007fff8917092d in -[NSView viewWillDraw] ()
#36 0x00007fff89170bed in __22-[NSView viewWillDraw]_block_invoke_0 ()
#37 0x00007fff884d50b6 in __NSArrayEnumerate ()
#38 0x00007fff8917092d in -[NSView viewWillDraw] ()
#39 0x00007fff8916ff84 in -[NSView _sendViewWillDrawInRect:clipRootView:] ()
#40 0x00007fff8913c3f1 in -[NSView displayIfNeeded] ()
#41 0x00007fff891f93f8 in -[NSWindow _reallyDoOrderWindow:relativeTo:findKey:forCounter:force:isModal:] ()
#42 0x00007fff891f8a18 in -[NSWindow _doOrderWindow:relativeTo:findKey:forCounter:force:isModal:] ()
#43 0x00007fff891f85ff in -[NSWindow orderWindow:relativeTo:] ()
#44 0x00007fff890f9c96 in -[NSIBObjectData nibInstantiateWithOwner:topLevelObjects:] ()
#45 0x00007fff890d8b7d in loadNib ()
#46 0x00007fff890d80a9 in +[NSBundle(NSNibLoading) _loadNibFile:nameTable:withZone:ownerBundle:] ()
#47 0x00007fff890d7ede in -[NSBundle(NSNibLoading) loadNibNamed:owner:topLevelObjects:] ()
#48 0x00007fff890d7cbe in +[NSBundle(NSNibLoading) loadNibNamed:owner:] ()
#49 0x00007fff890d447f in NSApplicationMain ()
#50 0x0000000100001432 in main

awakeFromNib方法不应该在viewController实例化后才调用吗？

Answer 1

根据我的经验，任何xib文档的文件所有者都会收到-awakeFromNib消息只要有新的文件 View 是从该 xib 文件加载的。正如您所注意到的，当基于 View 的 TableView 从 xib 文件创建新行时，就会发生这种情况。

我知道没有办法阻止这种情况发生，除非跟踪您调用 awakeFromNib 的次数并仅在第一次时执行初始化代码。

或者，更好将您的初始化逻辑放在另一个具有更可靠时序的方法中 - 例如在 -loadView 中，在调用 super 之后。我做了类似的事情:

- (void)loadView {
    [self vvViewWillLoad];
    [super loadView];
    [self vvViewDidLoad];
}

- (void)vvViewDidLoad {
    ... // initialization material here
}