[Deep dig] ViewController初始化过程调查

代码：https://github.com/xufeng79x/ViewControllerLife

1、简介：

　　介绍xib方式、storyborad方式以及code方式下ViewController的初始化过程。

2.实现

　　思路：

　　

主屏幕上三个按钮分别实现三种不同方式创建的viewcontroller。在各个view的实现中基本上按照如下结构来查看控制器的整个生成过程：下面代码以xib方式创建的controller为例子。

-(instancetype)init
{
    NSLog(@"MyViewController:init");
    self = [super init];
    return self;
}

-(instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    NSLog(@"xibController:initWithNibName the nibName = %@", nibNameOrNil);
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    return self;

}

- (instancetype)initWithCoder:(NSCoder *)coder
{
    NSLog(@"xibController:initWithCoder");
    self = [super initWithCoder:coder];
    return self;
}

-(void)awakeFromNib{
    NSLog(@"xibController:awakeFromNib");
}

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"xibController:viewDidLoad");

    // 用于证明 root view就是指向xib文件中的view
    [self.view performSelector:@selector(actionMyXibView)];
}

-(void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    NSLog(@"xibController:viewWillAppear");
}

-(void)viewWillLayoutSubviews{
    NSLog(@"xibController:viewWillLayoutSubviews");
}

-(void)viewDidLayoutSubviews{
    NSLog(@"xibController:viewDidLayoutSubviews");
}

-(void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    NSLog(@"xibController:viewDidAppear");
}

-(void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    NSLog(@"xibController:viewWillDisappear");
}

-(void)viewDidDisappear:(BOOL)animated{
    [super viewDidDisappear:animated];
    NSLog(@"xibController:viewDidDisappear");
}

当点击按钮的时候会创建controller并打印上述方法的日志，以此查看不同方式的不同初始化过程。

xib方式：此种方式定义可参考[How to]如何通过xib来自定义UIViewController

-- :::] Show ViewController!
2016-03-18 11:19:30.373 CreateViewControlerFromXib[1711:58126] MyViewController:init
2016-03-18 11:19:30.373 CreateViewControlerFromXib[1711:58126] xibController:initWithNibName the nibName = (null)
2016-03-18 11:19:30.376 CreateViewControlerFromXib[1711:58126] MyXibView:awakeFromNib
-- :::] xibController:viewDidLoad
2016-03-18 11:19:30.377 CreateViewControlerFromXib[1711:58126] I am a MyXibView instance!
-- :::] rootViewController:viewWillDisappear
-- :::] xibController:viewWillAppear
-- :::] xibController:viewWillLayoutSubviews
-- :::] xibController:viewDidLayoutSubviews
-- :::] rootViewController:viewWillLayoutSubviews
-- :::] rootViewController:viewDidLayoutSubviews
-- :::] xibController:viewWillLayoutSubviews
-- :::] xibController:viewDidLayoutSubviews
-- :::] xibController:viewDidAppear
-- :::] rootViewController:viewDidDisappear

结论：使用initWithNibName 作为初始化方法，不会触发自身的awakeFromNib但是会触发xib中定义的view的awakeFromNib方法

storyborad方式：

2016-03-18 11:27:10.659 CreateViewControlerFromXib[1779:62369] storyBoradController:initWithCoder
2016-03-18 11:27:10.659 CreateViewControlerFromXib[1779:62369] storyBoradController:awakeFromNib
2016-03-18 11:27:10.662 CreateViewControlerFromXib[1779:62369] MyStoryView:awakeFromNib
-- :::] storyBoradController:viewDidLoad
2016-03-18 11:27:10.662 CreateViewControlerFromXib[1779:62369] I am a MyStoryView instance!
-- :::] rootViewController:viewWillDisappear
-- :::] storyBoradController:viewWillAppear
-- :::] storyBoradController:viewWillLayoutSubviews
-- :::] storyBoradController:viewDidLayoutSubviews
-- :::] rootViewController:viewWillLayoutSubviews
-- :::] rootViewController:viewDidLayoutSubviews
-- :::] storyBoradController:viewWillLayoutSubviews
-- :::] storyBoradController:viewDidLayoutSubviews
-- :::] storyBoradController:viewDidAppear
-- :::] rootViewController:viewDidDisappear

结论：使用initWithCoder为初始化方法同时会触发自身和定义在文件中的view的awakeFromNib方法。

code方式：

2016-03-18 11:24:15.864 CreateViewControlerFromXib[1744:60562] CodeViewController:init
2016-03-18 11:24:15.864 CreateViewControlerFromXib[1744:60562] CodeViewController:initWithNibName the nibName = (null)
-- :::] CodeViewController:viewDidLoad
-- :::] rootViewController:viewWillDisappear
-- :::] CodeViewController:viewWillAppear
-- :::] CodeViewController:viewWillLayoutSubviews
-- :::] CodeViewController:viewDidLayoutSubviews
-- :::] rootViewController:viewWillLayoutSubviews
-- :::] rootViewController:viewDidLayoutSubviews
-- :::] CodeViewController:viewWillLayoutSubviews
-- :::] CodeViewController:viewDidLayoutSubviews
-- :::] CodeViewController:viewDidAppear
-- :::] rootViewController:viewDidDisappear

结论：使用initWithNibName作为初始化方法。不会触发自身的awakeFromNib方法。

其他结论：

1.viewDidLoad开始后面的初始化过程相同。

2.无论是storyborad方式还是xib方式，他们的rootview都是文件中定义的view，上述日志中的蓝色日志就是为了证明这一点。

对于rootview的初始化方式可以参考如下图：

当屏幕需要展示某个UiViewController的内容的时候会通过self.view方式获取此控制器的跟视图，默认的self.view会通过懒加载的方式去加载，也就是说一开始为nil的。当为nil的时候就会去

调用loadview方法来加载它，如何加载的参考上图。

完结。