承接上文iOS设计模式五(访问者,装饰,责任链)
本文为算法封装--获取源码

目录
1 模板模式
2 策略模式
3 命令模式

1 模板模式

模板模式顾名思义,套用模板.应该是最简单常用的模式了吧,就是俩字:复用!
继承也是复用的一种方式,在抽象类或者父类中定义公共的方法,在子类中重写或重载实现

稍微看个继承的代码😂
做一顿饭有很多选择,中餐,西餐.
父类OSZFood.h

#import <Foundation/Foundation.h>
@interface OSZFood : NSObject
//做饭
- (void)make;
//米饭
- (void)makeMeal;
//肉
- (void)makeMeat;
//蔬菜
- (void)makeVegetables;
//预留的空方法,子类去添加 所谓的"钩子"
- (void)makeOther;
@end

OSZFood.m

#import "OSZFood.h"
@implementation OSZFood
- (void)make{
    [self makeMeal];
    [self makeMeat];
    [self makeVegetables];
}
- (void)makeMeal{
    NSLog(@"做主食");
}
- (void)makeMeat{
    NSLog(@"做肉");
}
- (void)makeVegetables{
    NSLog(@"做菜");
}
- (void)makeOther{  
}
@end

中餐OSZChineseFood.h

#import "OSZFood.h"
@interface OSZChineseFood : OSZFood

//重写做菜方法,加入中餐特有的食物
- (void)makeVegetables;
- (void)chao;
@end

OSZChineseFood.m

#import "OSZChineseFood.h"
@implementation OSZChineseFood

//重写make方法,加入中餐特有的食物
- (void)makeVegetables{
    [self chao];
}
- (void)chao{
    NSLog(@"炒个菜");
}
@end

西餐 OSZWesternFood.h

#import "OSZFood.h"
@interface OSZWesternFood : OSZFood

//重写做肉方法,加入西餐特有的牛排
- (void)makeMeat;
- (void)steak;
@end

OSZWesternFood.m

#import "OSZWesternFood.h"
@implementation OSZWesternFood

- (void)makeMeat{
    [self steak];
}
- (void)steak{
    NSLog(@"煎个牛排");
}
@end

控制器OSZThirteenVC.m

#import "OSZThirteenVC.h"
#import "OSZChineseFood.h"
#import "OSZWesternFood.h"
@interface OSZThirteenVC ()
@end
@implementation OSZThirteenVC
- (void)viewDidLoad {
    [super viewDidLoad];
    OSZChineseFood *c = [[OSZChineseFood alloc]init];
    [c make];    //做主食  //做肉 //炒个菜

    OSZWesternFood *w = [[OSZWesternFood alloc]init];
    [w make];    //做主食  //煎个牛排  //做菜
}
@end

没什么可看的,就是个继承实现的简单复用,是抽出共同行为放入框架类中的基本手段

2 策略模式

策略模式的类结构

策略模式中一个关键角色是策略类strategy,它为所有支持的或相关的算法声明了一个共同接口,下面三个是具体策略类concreteStrategy,分别根据context的需求实现不同的效果,
调用时context使用strategy声明的方法,根据枚举值选用具体策略类concreteStrategy就可以了

看到这里是不是感觉很简单,其实我们在写app做一个界面的时候就自然的用到了,
context就是视图View,策略类就是控制器Controller,
我们复用同一个View,Controller调用不同的接口,或者干脆换个Controller,
在这个View上显示不同的控件(比如Label,按钮Button,或者自定义的控件),或者显示不同的数据Model

简单的MVC中策略模式例子:
做一个简单的视图,根据控制器不同显示不同的数据
OSZFourteenView.h

#import <UIKit/UIKit.h>
@interface OSZFourteenView : UIView
@property (nonatomic, weak) UILabel *lbl;
@property (nonatomic, weak) UIButton *btn;
@end

OSZFourteenView.m

#import "OSZFourteenView.h"
@implementation OSZFourteenView
- (instancetype)initWithFrame:(CGRect)frame{
    self = [super initWithFrame:frame];
    if (self){
        [self setupUI];
    }
    return self;
}

- (void)setupUI{
    self.backgroundColor = [UIColor whiteColor];
    
    CGRect rect = CGRectMake(100,100,150,30);
    UILabel *titleLbl = [[UILabel alloc]initWithFrame:rect];
    titleLbl.text = @"";
    titleLbl.textColor = [UIColor blackColor];
    titleLbl.font = [UIFont boldSystemFontOfSize:22];
    titleLbl.textAlignment = NSTextAlignmentCenter;
    [self addSubview:titleLbl];
    self.lbl = titleLbl;
    
    rect = CGRectMake(100,200,200,30);
    UIButton *button = [[UIButton alloc]initWithFrame:rect];
    [button setTitle:@"" forState:UIControlStateNormal];
    [button setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    button.titleLabel.font = [UIFont systemFontOfSize:22];
    [self addSubview:button];
    self.btn = button;
}
@end

两个控制器:
OSZFourteenVC.m

#import "OSZFourteenVC.h"
#import "OSZFourteenView.h"
#import "OSZFourteenVC2.h"
@interface OSZFourteenVC ()
@end

@implementation OSZFourteenVC
- (void)viewDidLoad {
    [super viewDidLoad];
    OSZFourteenView *view14 = [[OSZFourteenView alloc]init];
    self.view = view14;
    view14.lbl.text = @"第一个控制器";
    [view14.btn setTitle:@"跳到第二个控制器" forState:UIControlStateNormal];
    [view14.btn addTarget:self action:@selector(turn) forControlEvents:UIControlEventTouchUpInside];
}

- (void)turn{
    [self presentViewController:[[OSZFourteenVC2 alloc]init] animated:YES completion:nil];
}
@end

OSZFourteenVC2.m

#import "OSZFourteenVC2.h"
#import "OSZFourteenView.h"
#import "OSZFourteenVC.h"
@interface OSZFourteenVC2 ()
@end

@implementation OSZFourteenVC2

- (void)viewDidLoad {
    [super viewDidLoad];
    OSZFourteenView *view14 = [[OSZFourteenView alloc]init];
    self.view = view14;
    view14.lbl.text = @"第二个控制器";
    [view14.btn setTitle:@"跳到第一个控制器" forState:UIControlStateNormal];
    [view14.btn addTarget:self action:@selector(turn) forControlEvents:UIControlEventTouchUpInside];
}

- (void)turn{
    [self dismissViewControllerAnimated:YES completion:nil];
}
@end

策略模式与装饰模式看起来有点像,但是装饰器是在对象外面叠加,而策略模式是在内部更换内容

3 命令模式

把指令封装在命令对象中,命令对象可以被传递并且被不同的客户端复用,客户端可以把它参数化并置入队列或日志中
命令模式消除了作为对象的动作和执行它的接收器之间的绑定.

看完了概念是不是感觉似曾相识?
实际上命令模式是Cocoa Touch框架收录的模式之一
NSInvocation与NSUndoManager和"目标-动作"机制是框架中对这个模式的典型应用

NSInvocation对象封装运行时库以向接收器转发执行消息所需的所有必要信息,是调用方法的一种方式
NSUndoManager作为通用的撤销栈的管理类,能够逆转,撤销操作
"目标-动作"机制就是 目标(Target)与动作(Action),即用performSelector调用方法的一种方式

一个用NSUndoManager实现的支持撤销功能的画板:

定义线OSZLine.h

#import <Foundation/Foundation.h>
@interface OSZLine : NSObject

@property (nonatomic,assign) CGPoint begin;
@property (nonatomic,assign) CGPoint end;
@property (nonatomic,strong) UIColor *color;

@end

OSZLine.m

#import "OSZLine.h"
@implementation OSZLine
-(instancetype)init{
    self = [super init];
    if (self) {
        [self setColor:[UIColor blackColor]];
    }
    return self;
}
@end

画板OSZDrawView.h

#import <UIKit/UIKit.h>
#import "OSZLine.h"
@interface OSZDrawView : UIView

@property (nonatomic) OSZLine *currentLine;
@property (nonatomic) NSMutableArray *linesCompleted;
//回退
@property (nonatomic, weak) UIButton *undoBtn;
//前进
@property (nonatomic, weak) UIButton *redoBtn;

@end

OSZDrawView.m

#import "OSZDrawView.h"

@implementation OSZDrawView

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        [self setupUI];
    }
    return self;
}

- (void)setupUI
{
    self.backgroundColor = [UIColor whiteColor];
    self.linesCompleted = [[NSMutableArray alloc] init];
    [self setMultipleTouchEnabled:YES];
    
    [self becomeFirstResponder];
    
    CGFloat origin = 40;
    CGFloat W = (kScreenWidth - 4 * origin ) * 0.5;
    CGFloat H = 44;
    CGFloat X = origin;
    CGFloat Y = kScreenHeight - origin - H;
    CGRect rect = CGRectMake(X,Y,W,H);
    UIButton *undoBtn = [[UIButton alloc]initWithFrame:rect];
    [undoBtn setTitle:@"回退" forState:UIControlStateNormal];
    [undoBtn setBackgroundColor:[UIColor grayColor]];
    [undoBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    undoBtn.titleLabel.font = [UIFont systemFontOfSize:17];
    undoBtn.layer.cornerRadius = 5;
    undoBtn.layer.masksToBounds = YES;
    self.undoBtn = undoBtn;
    [self addSubview:undoBtn];
    [self.undoBtn addTarget:self action:@selector(undo) forControlEvents:UIControlEventTouchUpInside];
    
    X = 3 * origin + W;
    rect = CGRectMake(X,Y,W,H);
    UIButton *redoBtn = [[UIButton alloc]initWithFrame:rect];
    [redoBtn setTitle:@"前进" forState:UIControlStateNormal];
    [redoBtn setBackgroundColor:[UIColor grayColor]];
    [redoBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    redoBtn.titleLabel.font = [UIFont systemFontOfSize:17];
    redoBtn.layer.cornerRadius = 5;
    redoBtn.layer.masksToBounds = YES;
    self.undoBtn = redoBtn;
    [self addSubview:redoBtn];
    [self.undoBtn addTarget:self action:@selector(redo) forControlEvents:UIControlEventTouchUpInside];
}


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGContextSetLineWidth(context, 5.0);
    CGContextSetLineCap(context, kCGLineCapRound);
    for (OSZLine *line in self.linesCompleted) {
        [[line color] set];
        CGContextMoveToPoint(context, [line begin].x, [line begin].y);
        CGContextAddLineToPoint(context, [line end].x, [line end].y);
        CGContextStrokePath(context);
    }
}

//回退
- (void)undo
{
    if ([self.undoManager canUndo]) {
        [self.undoManager undo];
    }
}

//前进
- (void)redo
{
    if ([self.undoManager canRedo]) {
        [self.undoManager redo];
    }
}

//NSUndoManager 的实现原理是它作为一个记录器，每次数据变化，我们要用这个记录器记录一个相反的操作，
//当需要undo的时候，它通过执行这个相反的操作就可以实现了。
- (void)addLine:(OSZLine*)line
{
    [[self.undoManager prepareWithInvocationTarget:self] removeLine:line];
    [self.linesCompleted addObject:line];
    [self setNeedsDisplay];
}

- (void)removeLine:(OSZLine*)line
{
    if ([self.linesCompleted containsObject:line]) {
        [[self.undoManager prepareWithInvocationTarget:self] addLine:line];
        [self.linesCompleted removeObject:line];
        [self setNeedsDisplay];
    }
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    for (UITouch *t in touches)
    {
        CGPoint loc = [t locationInView:self];
        self.currentLine.end = loc;
        
        if (self.currentLine)
        {
            [self addLine:self.currentLine];
        }
        OSZLine *newLine = [[OSZLine alloc] init];
        newLine.begin = loc;
        newLine.end = loc;
        self.currentLine = newLine;
    }
}



- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    //NSUndoManager有一个分组的概念，就是为了解决这类问题的
    //将所有的笔画放在一个组中
    [self.undoManager beginUndoGrouping];
    for (UITouch *t in touches) {
        // Create a line for the value
        CGPoint loc = [t locationInView:self];
        OSZLine *newLine = [[OSZLine alloc] init];
        newLine.begin = loc;
        newLine.end = loc;
        self.currentLine = newLine;
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self setNeedsDisplay];
    [self.undoManager endUndoGrouping];
}

@end

控制器OSZFifteenVC.m

#import "OSZFifteenVC.h"
#import "OSZDrawView.h"

@interface OSZFifteenVC ()

@property (nonatomic, weak) OSZDrawView *drawView;

@end

@implementation OSZFifteenVC

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    
    //NSUndoManager应用
    OSZDrawView *drawView = [[OSZDrawView alloc]initWithFrame:self.view.frame];
    self.drawView = drawView;
    [self.view addSubview:drawView];
    
    //NSInvocation应用
    [self invocationMethod];
    
    //所谓的"目标-动作"机制就是 目标(Target)与动作(Action)
    [self performSelector:@selector(invocationMethod)];
}

//命令模式是Cocoa Touch框架收录的模式之一
//NSInvocation与NSUndoManager和"目标-动作"机制是框架中对这个模式的典型应用
- (void)invocationMethod
{
    //NSInvocation;用来包装方法和对应的对象，它可以存储方法的名称，对应的对象，对应的参数,
    /*
     NSMethodSignature：签名：再创建NSMethodSignature的时候，必须传递一个签名对象，签名对象的作用：用于获取参数的个数和方法的返回值
     */
    //创建签名对象的时候不是使用NSMethodSignature这个类创建，而是方法属于谁就用谁来创建
    NSMethodSignature*signature = [OSZFifteenVC instanceMethodSignatureForSelector:@selector(sendMessageWithNumber:WithContent:)];
    //1、创建NSInvocation对象
    NSInvocation*invocation = [NSInvocation invocationWithMethodSignature:signature];
    invocation.target = self;
    //invocation中的方法必须和签名中的方法一致。
    invocation.selector = @selector(sendMessageWithNumber:WithContent:);
    /*第一个参数：需要给指定方法传递的值
     第一个参数需要接收一个指针，也就是传递值的时候需要传递地址*/
    //第二个参数：需要给指定方法的第几个参数传值
    NSString*number = @"13812345678";
    //注意：设置参数的索引时不能从0开始，因为0已经被self占用，1已经被_cmd占用
    [invocation setArgument:&number atIndex:2];
    NSString*number2 = @"哈哈哈";
    [invocation setArgument:&number2 atIndex:3];
    //2、调用NSInvocation对象的invoke方法
    //只要调用invocation的invoke方法，就代表需要执行NSInvocation对象中制定对象的指定方法，并且传递指定的参数
    [invocation invoke];
}

- (void)sendMessageWithNumber:(NSString*)number WithContent:(NSString*)content{
    NSLog(@"电话号%@,姓名%@",number,content);
}
@end

扩展:
iOS: 为画板App增加 Undo/Redo(撤销/重做)操作