极客班 iOS 设计模式（三）

设计模式课程给我的感受是：理清各种平时固定用的 API 的背后的原理或思路，尤其是写代码时候反复去审视开发框架和思路都有一定的帮助。

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

11. 层次结构

动机：

• 对象之间关系
• 允许一组相互协作的对象当成单⼀对象处理
• 无需⼦类化,实现⾃定义
• 降低 parents class 复杂度
• 使用 tree 结构,⽅便数据的存储,操作和搜索

Layers associated with a window View Hierarchy in Xcode

其实还有更强大的工具：Reveal，附使用方法。

节选自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 负责界⾯显示和事件处理
• CALayer 负责屏幕渲染(Layer Tree)
• View/Layer 的变化需要通过渲染器实时渲染到屏幕上
• layer.presentationLayer

The layer trees for a window

延伸阅读：

• View Programming Guide for iOS
• Debug View Hierarchy
• Core Animation Basics

12. 响应链（Responder Chain）

The responder chain on iOS

节选自 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

延伸阅读：

• Event Handling Guide for iOS

13. Prototype

如 UITableView 的 Prototype Cells：

• 原型对象的基本特征是可以被复制 NSCopy 和 NSCoding 协议
• 可以利用界面⼯具和支持复制的类确保互操作性
• 原型对象使用深复制
• 利用 NSKeyedArchiver 和 NSKeyedUnarchiver 实现深复制

总结

• MVC,target-action
• 两步创建，模版模式
• 委托模式，观察者模式，消息通知，KVC/KVO
• 归档和解档(Serialization)，复制模式
• 层次结构，响应链
• prototype

完