问题描述
任何人知道为什么此根查看控制器的 viewDidLoad 在启动时被调用两次？
Anyone know why this root View Controller's viewDidLoad is being called twice at launch? It's driving me nuts!
这是从第一次到 viewDidLoad 的堆栈跟踪：
here's the stack trace from first time through viewDidLoad:
#0 0x0000276a in -[RootViewController viewDidLoad] at RootViewController.m:71
#1 0x3097548f in -[UIViewController view]
#2 0x00002734 in -[RootViewController initWithCoder:] at RootViewController.m:39
#3 0x30ab5ce4 in -[UIClassSwapper initWithCoder:]
#4 0x30514636 in _decodeObjectBinary
#5 0x30514035 in _decodeObject
#6 0x30ab5a1d in -[UIRuntimeConnection initWithCoder:]
#7 0x30514636 in _decodeObjectBinary
#8 0x30515f27 in -[NSKeyedUnarchiver _decodeArrayOfObjectsForKey:]
#9 0x305163b0 in -[NSArray(NSArray) initWithCoder:]
#10 0x30514636 in _decodeObjectBinary
#11 0x30514035 in _decodeObject
#12 0x30ab4dde in -[UINib instantiateWithOptions:owner:loadingResourcesFromBundle:]
#13 0x30ab6eb3 in -[NSBundle(NSBundleAdditions) loadNibNamed:owner:options:]
#14 0x308f85f1 in -[UIApplication _loadMainNibFile]
#15 0x30901a15 in -[UIApplication _runWithURL:sourceBundleID:]
#16 0x308fef33 in -[UIApplication handleEvent:withNewEvent:]
#17 0x308fad82 in -[UIApplication sendEvent:]
#18 0x309013e1 in _UIApplicationHandleEvent
#19 0x32046375 in PurpleEventCallback
#20 0x30245560 in CFRunLoopRunSpecific
#21 0x30244628 in CFRunLoopRunInMode
#22 0x308f930d in -[UIApplication _run]
#23 0x309021ee in UIApplicationMain
#24 0x000022e4 in main at main.m:14
，第二次：
#0 0x0000276a in -[RootViewController viewDidLoad] at RootViewController.m:71
#1 0x30ab50cd in -[UINib instantiateWithOptions:owner:loadingResourcesFromBundle:]
#2 0x30ab6eb3 in -[NSBundle(NSBundleAdditions) loadNibNamed:owner:options:]
#3 0x308f85f1 in -[UIApplication _loadMainNibFile]
#4 0x30901a15 in -[UIApplication _runWithURL:sourceBundleID:]
#5 0x308fef33 in -[UIApplication handleEvent:withNewEvent:]
#6 0x308fad82 in -[UIApplication sendEvent:]
#7 0x309013e1 in _UIApplicationHandleEvent
#8 0x32046375 in PurpleEventCallback
#9 0x30245560 in CFRunLoopRunSpecific
#10 0x30244628 in CFRunLoopRunInMode
#11 0x308f930d in -[UIApplication _run]
#12 0x309021ee in UIApplicationMain
#13 0x000022e4 in main at main.m:14
推荐答案
很奇怪。我没有看到这种特殊情况，但一般来说，你应该假设viewDidLoad可以被多次调用。每当引用该控制器的nib文件被加载时，它都会被调用。
Weird. I haven't seen this particular case, but in general, you ought to assume that viewDidLoad can be called multiple times. It'll get called whenever a nib file that references that controller gets loaded.
对于只有一个nib的简单应用程序，不应该发生。但在一个更复杂的应用程序中，可以加载和卸载视图控制器，这一切都会发生。
For a simple app with only one nib, that shouldn't happen. But in a more-complex app that can load and unload view controllers, this happens all the time.
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