@PRoperty (nonatomic, readonly) NSTextStorage *textStorage;//注意為只讀屬性，因此不能直接更改內容，NSTextStorage為NSMutableAttributeString的子類，因此可以更改字符串屬性內容（而非字符串）//例如，添加屬性[self.body.textStorage addAttribute:NSForegroundColorAttributeName                                  value:sender.backgroundColor                                  range:self.body.selectedRange];@property (nonatomic, strong) UIFont *font;//例如添加字體self.body.font = [UIFont preferredFontForTextStyle:UIFontTextStyleBody];    self.headLine.font = [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];//文本布局功能，如圖文混排等@property (readonly) NSTextContainer *textContainer;@property (readonly) NSLayoutManager *layoutManager;

- (instancetype)initWithNibName:(NSString *)name bundle:(NSBundle *)bundle;//非storyboard加載方式，指定初始化器- (void)awakeFromNib;//從storyboard中加載UI時調用，此時未設置輸出口//設置輸出口- (void)viewDidLoad;//可以放置控制器初始化代碼（一次性），如init。不可放置與幾何相關的代碼，此時控制器中的UI邊界未確定//確定幾何布局//當視圖frame發生變化時就會被調用，此處適合添加與幾何相關的代碼- (void)viewWillLayoutSubviews;- (void)viewDidLayoutSubviews;//其他關于屏幕旋轉等API...- (void)viewWillAppear:(BOOL)animated;//生命周期中可能會被反復調用，因此不能放置一次性初始化內容- (void)viewDidAppear:(BOOL)animated;- (void)viewWillDisappear:(BOOL)animated;//可以進行一些當前數據保存工作- (void)viewDidDisappear:(BOOL)animated;- (void)didReceiveMemoryWarning;//系統在內存不足時調用

[NSNotificationCenter defaultCenter];//獲取defaultCenter//添加觀察者- (void)addObserver:(id)observer //接收通知的對象                  selector:(SEL)methodToInvokeIfsomethingHappens                     name:(NSString *)name //廣播名                    object:(id)sender; //監聽的廣播對象，nil指監聽所有對象//接收到通知后調用方法- (void)methodToInvokeIfSomethingHappens:(NSNotification *)notification{    notification.name // the name passed above    notification.object //發送廣播的對象    notification.userInfo // notification-specific information about what happened（取決于發送者）}//結束收聽通知，通常放于視圖從界面消失時[center removeObserver:self];[center removeObserver:self name:UIContentSizeCategoryDidChangeNotification object:nil];    

//視圖出現在屏幕上注冊通知- (void)viewWillAppear:(BOOL)animated{    [super viewWillAppear:animated];    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(preferredFontChanged:) name:UIContentSizeCategoryDidChangeNotification object:nil];}//通知出現時調用方法- (void)preferredFontChanged:(NSNotification *)notification{    [self usePreferredFonts];}//重新設置字體- (void)usePreferredFonts{    self.body.font = [UIFont preferredFontForTextStyle:UIFontTextStyleBody];    self.headLine.font = [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];}//視圖離開界面是移除通知- (void)viewWillDisappear:(BOOL)animated{    [super viewWillDisappear:animated];    [[NSNotificationCenter defaultCenter] removeObserver:self                                                    name:UIContentSizeCategoryDidChangeNotification                                                  object:nil];