將相關代碼添加打印献丑。

- (instancetype)init{
    if (self = [super init]) {
        NSLog(@"%s",__func__);
    }
    return self;
}

//通過代碼創(chuàng)建控件就會調用這個方法
- (instancetype)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        NSLog(@"%s",__func__);
    }
    return self;
}

//通過storyboared或者xib中創(chuàng)建控件就會調用這個方法
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super initWithCoder:aDecoder]) {
        NSLog(@"%s",__func__);
    }
    return self;
}

- (void)awakeFromNib {
    [super awakeFromNib];
    NSLog(@"%s",__func__);
}

//如果在initWithFrame中添加子視圖會調用兩次
- (void)layoutSubviews{
    [super layoutSubviews];
        NSLog(@"%s",__func__);
}

- (void)didAddSubview:(UIView *)subview{
    [super didAddSubview:subview];
        NSLog(@"%s",__func__);
}

- (void)willRemoveSubview:(UIView *)subview{
    [super willRemoveSubview:subview];
        NSLog(@"%s",__func__);
}

- (void)willMoveToSuperview:(nullable UIView *)newSuperview{
    [super willMoveToSuperview:newSuperview];
        NSLog(@"%s",__func__);
}

- (void)didMoveToSuperview{
    [super didMoveToSuperview];
        NSLog(@"%s",__func__);
}

- (void)willMoveToWindow:(nullable UIWindow *)newWindow{
    [super willMoveToWindow:newWindow];
        NSLog(@"%s",__func__);
}

- (void)didMoveToWindow{
    [super didMoveToWindow];
        NSLog(@"%s",__func__);
}

- (void)removeFromSuperview{
    [super removeFromSuperview];
        NSLog(@"%s",__func__);
}

- (void)dealloc{
        NSLog(@"%s",__func__);
}

當創(chuàng)建view時

2017-11-06 10:35:12.347153+0800 IOSLife[7587:2353869] -[MyView willMoveToSuperview:]
2017-11-06 10:35:12.347312+0800 IOSLife[7587:2353869] -[MyView didMoveToSuperview]
2017-11-06 10:35:12.353483+0800 IOSLife[7587:2353869] -[MyView willMoveToWindow:]
2017-11-06 10:35:12.353644+0800 IOSLife[7587:2353869] -[MyView didMoveToWindow]
2017-11-06 10:35:12.363861+0800 IOSLife[7587:2353869] -[MyView layoutSubviews]
2017-11-06 10:35:12.655946+0800 IOSLife[7607:2356750] -[MyView drawRect:]

當view銷毀時

2017-11-06 10:41:28.152448+0800 IOSLife[7607:2356750] -[MyView willMoveToWindow:]
2017-11-06 10:41:28.152693+0800 IOSLife[7607:2356750] -[MyView didMoveToWindow]
2017-11-06 10:41:28.155160+0800 IOSLife[7607:2356750] -[MyView willMoveToSuperview:]
2017-11-06 10:41:28.155281+0800 IOSLife[7607:2356750] -[MyView didMoveToSuperview]
2017-11-06 10:41:28.155336+0800 IOSLife[7607:2356750] -[MyView removeFromSuperview]
2017-11-06 10:41:28.155399+0800 IOSLife[7607:2356750] -[MyView dealloc]

可以看出上面方法中只會執(zhí)行一次的方法有removeFromSuperview诫硕、dealloc兩個方法(layoutSubviews在子視圖布局變動時會多次調用)溺职，所以可以在這兩個方法中執(zhí)行釋放內存等操作(e.g:移除觀察者姜贡，定時器等)冯吓。

給view添加子視圖時

2017-11-06 10:45:47.749310+0800 IOSLife[7614:2358053] -[MyView didAddSubview:]
2017-11-06 10:45:47.750111+0800 IOSLife[7614:2358053] -[MyView layoutSubviews]

didAddSubview:和willRemoveSubview:需要有子視圖才能執(zhí)行儡率。

此時再銷毀該view

2017-11-06 10:46:28.022473+0800 IOSLife[7617:2358497] -[MyView willMoveToSuperview:]
2017-11-06 10:46:28.022643+0800 IOSLife[7617:2358497] -[MyView didMoveToSuperview]
2017-11-06 10:46:28.031533+0800 IOSLife[7617:2358497] -[MyView willMoveToWindow:]
2017-11-06 10:46:28.031738+0800 IOSLife[7617:2358497] -[MyView didMoveToWindow]
2017-11-06 10:46:28.036048+0800 IOSLife[7617:2358497] -[MyView layoutSubviews]
2017-11-06 10:46:28.719103+0800 IOSLife[7617:2358497] -[MyView didAddSubview:]
2017-11-06 10:46:28.719873+0800 IOSLife[7617:2358497] -[MyView layoutSubviews]
2017-11-06 10:46:30.529769+0800 IOSLife[7617:2358497] -[MyView willMoveToWindow:]
2017-11-06 10:46:30.530059+0800 IOSLife[7617:2358497] -[MyView didMoveToWindow]
2017-11-06 10:46:30.532931+0800 IOSLife[7617:2358497] -[MyView willMoveToSuperview:]
2017-11-06 10:46:30.533055+0800 IOSLife[7617:2358497] -[MyView didMoveToSuperview]
2017-11-06 10:46:30.533112+0800 IOSLife[7617:2358497] -[MyView removeFromSuperview]
2017-11-06 10:46:30.533183+0800 IOSLife[7617:2358497] -[MyView dealloc]
2017-11-06 10:46:30.533256+0800 IOSLife[7617:2358497] -[MyView willRemoveSubview:]

willRemoveSubview是在dealloc后面執(zhí)行的。如果有多個子視圖胖喳，willRemoveSubview會循環(huán)執(zhí)行泡躯，直到移除所有子視圖。

注意：

• - (void)willMoveToSuperview:(nullable UIView *)newSuperview;和- (void)willMoveToWindow:(nullable UIWindow *)newWindow;這倆個方法可以根據(jù)參數(shù)判斷丽焊，nil則為銷毀较剃，否則為創(chuàng)建；
• - (void)didMoveToSuperview;和- (void)didMoveToWindow;可以根據(jù)self.superview判斷技健，nil則為銷毀写穴，否則為創(chuàng)建。
• 如果在initWithFrame中有view的初始化相關操作雌贱，layoutSubviews會調用兩次确垫。layoutSubviews只進行布局相關處理，不能有view初始化操作（當子視圖布局改變時會調用帽芽，能多次調用）删掀，下面是layoutSubviews的觸發(fā)條件:
  1、init初始化不會觸發(fā)layoutSubviews,但是是用initWithFrame進行初始化時导街，當rect的值不為CGRectZero時,也會觸發(fā)披泪。
  2、addSubview會觸發(fā)layoutSubviews搬瑰。
  3款票、設置view的Frame會觸發(fā)layoutSubviews控硼，當然前提是frame的值設置前后發(fā)生了變化。
  4艾少、滾動一個UIScrollView會觸發(fā)layoutSubviews卡乾。
  5、旋轉Screen會觸發(fā)父UIView上的layoutSubviews缚够。
  6幔妨、改變一個UIView大小的時候也會觸發(fā)父UIView上的layoutSubviews。