NSTableView 的委托在创建行时收到 awakeFromNib 消息



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,里面有一个基于视图的NSTableView。NSViewController子类实现协议NSTableViewDelegate,并且在IB中,NSTableView的委托连接到文件的所有者。当视图由绑定创建时,viewController的wakeFromNib方法将使用以下调用堆栈进行调用:

#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

wakeFromNib方法不应该只在viewController实例化后调用?

根据我的经验,任何xib文档File's Owner在从该xib文件加载新视图时都会收到一条-awakeFromNib消息。正如您所注意到的,当基于视图的表视图从xib文件创建新行时,会发生这种情况。

我不知道有什么方法可以阻止这种情况的发生,除了记录您调用awakeFromNib的次数,并只在第一次执行初始化代码。

或者更好的是,将初始化逻辑放在另一个定时更稳定的方法中,例如在-loadView中,在调用super之后。我做了一些类似的事情:

- (void)loadView {
    [self vvViewWillLoad];
    [super loadView];
    [self vvViewDidLoad];
}
- (void)vvViewDidLoad {
    ... // initialization material here
}

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