iOS生命周期调动系统函数过程：

有Storyboard

[ViewController load]

[ViewController initWithCoder:]

[ViewController awakeFromNib]

[ViewController loadView]

[ViewController viewDidLoad]

[ViewController viewWillAppear:]

[ViewController viewWillLayoutSubviews]

[ViewController viewDidLayoutSubviews]

[ViewController viewDidAppear:]

无storyboard

[ViewController load]

[ViewController initWithNibName:bundle:]

[ViewController init]

[ViewController loadView]

[ViewController viewDidLoad]

[ViewController viewWillAppear:]

[ViewController viewWillLayoutSubviews]

[ViewController viewDidLayoutSubviews]

[ViewController viewDidAppear:]

举例子：AViewController push到 BViewController：

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