ViewController加载过程（ShowViewCycle是ViewController.view的subView）：
1. -[ViewController initWithNibName:bundle:] [Line 82] nibNameOrNil:(null), nibBundleOrNil:(null)
ViewController初始化方法:
参数nibBundleOrNil：指定nib文件搜索的bundle，默认位mainBundle
参数nibNameOrNil：指定nib文件的名称，如果不指定，则先搜索View.nib，再搜索 ViewController.nib
2. -[ViewController loadView] [Line 100]
在self.view==nil的条件下调用
2.1 -[ViewController willMoveToParentViewController:] [Line 363]
2.2 -[ShowViewCycle initWithFrame:] [Line 49]
2.3 -[ShowViewCycle setNeedsDisplay] [Line 259]
ShowViewCycle的属性改变都会触发setNeedsDisplay
2.4 -[ShowViewCycle setNeedsDisplay] [Line 259]
2.5 -[ShowViewCycle setNeedsDisplay] [Line 259]
2.6 -[ShowViewCycle willMoveToSuperview:] [Line 174]
2.7 -[ShowViewCycle didMoveToSuperview] [Line 181]
2.8 -[ShowViewCycle setTranslatesAutoresizingMaskIntoConstraints:]
mas_makeConstraints主动触发
2.9 -[ShowViewCycle isDescendantOfView:] [Line 200]
addConstraint，会触发该判定，判定一个view是否是另一个view的subview
2.10-[ShowViewCycle isDescendantOfView:] [Line 200]
2.11-[ShowViewCycle isDescendantOfView:] [Line 200]
2.12-[ShowViewCycle isDescendantOfView:] [Line 200]
3. -[ViewController viewDidLoad] [Line 107]
3.1 -[ViewController shouldAutomaticallyForwardAppearanceMethods] [Line 336]
返回值如果是NO，子类必须重写- viewWillAppear: -viewDidAppear: -viewWillDisappear: -viewDidDisappear: -willRotateToInterfaceOrientation:duration: -willAnimateRotationToInterfaceOrientation:duration: -didRotateFromInterfaceOrientation:方法
4. -[ViewController viewWillAppear:] [Line 159]
4.1 -[ViewController beginAppearanceTransition:animated:] [Line 298]
4.2 -[ViewController shouldAutomaticallyForwardAppearanceMethods] [Line 336]
4.3 -[ShowViewCycle willMoveToWindow:] [Line 188]
4.4 -[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.5 -[ShowViewCycle needsUpdateConstraints] [Line 375]
4.6 -[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.7 -[ShowViewCycle isDescendantOfView:]
4.8 -[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.9 -[ShowViewCycle isDescendantOfView:] [Line 200]
4.10-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.11-[ShowViewCycle isDescendantOfView:] [Line 200]
4.12-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.13-[ShowViewCycle isDescendantOfView:] [Line 200]
4.14-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.15-[ShowViewCycle didMoveToWindow] [Line 195]
4.16-[ViewController viewWillLayoutSubviews] [Line 188]
4.17-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.18-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.19-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.20-[ShowViewCycle intrinsicContentSize] [Line 451]
内在内容的大小
4.21-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.22-[ShowViewCycle updateConstraints] [Line 370]
4.23-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.24-[ShowViewCycle alignmentRectInsets] [Line 434]
4.25-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.26-[ShowViewCycle alignmentRectInsets] [Line 434]
4.27-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.28-[ShowViewCycle alignmentRectInsets] [Line 434]
4.29-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.30-[ShowViewCycle alignmentRectInsets] [Line 434]
4.31-[ViewController updateViewConstraints] [Line 387]
4.32-[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
4.33-[ShowViewCycle alignmentRectInsets] [Line 434]
4.34-[ViewController viewDidLayoutSubviews] [Line 196]
4.35-[ShowViewCycle layoutSubviews] [Line 231]
4.36-[ShowViewCycle drawRect:] [Line 252]
4.37-[ViewController shouldAutomaticallyForwardAppearanceMethods] [Line 336]
5. -[ViewController viewDidAppear:] [Line 166]
5.1 -[ViewController didMoveToParentViewController:] [Line 370]
5.2 -[ViewController viewWillLayoutSubviews] [Line 188]
5.3 -[ViewController updateViewConstraints] [Line 387]
5.4 -[ShowViewCycle translatesAutoresizingMaskIntoConstraints] [Line 393]
5.5 -[ShowViewCycle alignmentRectInsets] [Line 434]
5.6 -[ViewController viewDidLayoutSubviews] [Line 196]