極客班 iOS 設計模式(三)

設計模式課程給我的感受是:理清各種平時固定用的 API 的背后的原理或思路,尤其是寫代碼時候反復去審視開發框架和思路都有一定的幫助。

課件下載:
https://github.com/gewill/GeekBand-iOS-Demo/tree/master/Design%20Patterns

11. 層次結構

動機:

  • 對象之間關系
  • 允許一組相互協作的對象當成單?對象處理
  • 無需?類化,實現?定義
  • 降低 parents class 復雜度
  • 使用 tree 結構,?便數據的存儲,操作和搜索
Layers associated with a window
Layers associated with a window
View Hierarchy in Xcode
View Hierarchy in Xcode

其實還有更強大的工具:Reveal,附使用方法

節選自UIView.h

@interface UIView(UIViewHierarchy)

@property(nonatomic,readonly) UIView       *superview;
@property(nonatomic,readonly,copy) NSArray *subviews;
@property(nonatomic,readonly) UIWindow     *window;

- (void)removeFromSuperview;
- (void)insertSubview:(UIView *)view atIndex:(NSInteger)index;
- (void)exchangeSubviewAtIndex:(NSInteger)index1 withSubviewAtIndex:(NSInteger)index2;

- (void)addSubview:(UIView *)view;
- (void)insertSubview:(UIView *)view belowSubview:(UIView *)siblingSubview;
- (void)insertSubview:(UIView *)view aboveSubview:(UIView *)siblingSubview;

- (void)bringSubviewToFront:(UIView *)view;
- (void)sendSubviewToBack:(UIView *)view;

- (void)didAddSubview:(UIView *)subview;
- (void)willRemoveSubview:(UIView *)subview;

- (void)willMoveToSuperview:(UIView *)newSuperview;
- (void)didMoveToSuperview;
- (void)willMoveToWindow:(UIWindow *)newWindow;
- (void)didMoveToWindow;

- (BOOL)isDescendantOfView:(UIView *)view;  // returns YES for self.
- (UIView *)viewWithTag:(NSInteger)tag;     // recursive search. includes self

// Allows you to perform layout before the drawing cycle happens. -layoutIfNeeded forces layout early
- (void)setNeedsLayout;
- (void)layoutIfNeeded;

iOS rendering tree:

  • UIView 負責界?顯示和事件處理
  • CALayer 負責屏幕渲染(Layer Tree)
  • View/Layer 的變化需要通過渲染器實時渲染到屏幕上
  • layer.presentationLayer
The layer trees for a window
The layer trees for a window

延伸閱讀:

12. 響應鏈(Responder Chain)

The responder chain on iOS
The responder chain on iOS

節選自 UIResponder.h

NS_CLASS_AVAILABLE_IOS(2_0) @interface UIResponder : NSObject {
  @private
}

- (UIResponder*)nextResponder;

- (BOOL)canBecomeFirstResponder;    // default is NO
- (BOOL)becomeFirstResponder;

- (BOOL)canResignFirstResponder;    // default is YES
- (BOOL)resignFirstResponder;

- (BOOL)isFirstResponder;

// Generally, all responders which do custom touch handling should override all four of these methods.
// Your responder will receive either touchesEnded:withEvent: or touchesCancelled:withEvent: for each
// touch it is handling (those touches it received in touchesBegan:withEvent:).
// *** You must handle cancelled touches to ensure correct behavior in your application.  Failure to
// do so is very likely to lead to incorrect behavior or crashes.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;

- (void)motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);
- (void)motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);
- (void)motionCancelled:(UIEventSubtype)motion withEvent:(UIEvent *)event NS_AVAILABLE_IOS(3_0);

- (void)remoteControlReceivedWithEvent:(UIEvent *)event NS_AVAILABLE_IOS(4_0);

- (BOOL)canPerformAction:(SEL)action withSender:(id)sender NS_AVAILABLE_IOS(3_0);
// Allows an action to be forwarded to another target. By default checks -canPerformAction:withSender: to either return self, or go up the responder chain.
- (id)targetForAction:(SEL)action withSender:(id)sender NS_AVAILABLE_IOS(7_0);
UIKit Inheritance
UIKit Inheritance

延伸閱讀:

13. Prototype

如 UITableView 的 Prototype Cells:

  • 原型對象的基本特征是可以被復制 NSCopy 和 NSCoding 協議
  • 可以利用界面?具和支持復制的類確保互操作性
  • 原型對象使用深復制
  • 利用 NSKeyedArchiver 和 NSKeyedUnarchiver 實現深復制

總結

  • MVC,target-action
  • 兩步創建,模版模式
  • 委托模式,觀察者模式,消息通知,KVC/KVO
  • 歸檔和解檔(Serialization),復制模式
  • 層次結構,響應鏈
  • prototype

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