iOS底層原理（十）架構設計-有解無憂

iOS中的幾種常用架構

MVC

MVC架構是以Model、Controller、View三者之間的關系來依賴的

Apple版的MVC

Apple最早的MVC的資料流向是以Controller為中心，在Model和View中間作為橋梁來銜接，而且Controller和Model、View之間的資料流向都是雙向的

-w651

例如，View上通過按鈕的點擊傳遞給Controller，Controller就去獲取資料來作為Model；Model的資料有了改變，又要通過展示到Controller展示到View上

三者的互動程序中，View和Model是互相沒有直接關聯的

在iOS程式中最常見的就是tableview的展示，見示例代碼

// LLNews
@interface LLNews : NSObject

@property (copy, nonatomic) NSString *title;
@property (copy, nonatomic) NSString *content;
@end

@implementation LLNews

@end

// LLNewsViewController
@interface LLNewsViewController : UITableViewController

@end

@interface LLNewsViewController ()
@property (strong, nonatomic) NSMutableArray *newsData;
@end

@implementation LLNewsViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self loadNewsData];
}

- (void)loadNewsData
{
    self.newsData = https://www.cnblogs.com/funkyRay/p/[NSMutableArray array];
    
    for (int i = 0; i < 20; i++) {
        LLNews *news = [[LLNews alloc] init];
        news.title = [NSString stringWithFormat:@"news-title-%d", i];
        news.content = [NSString stringWithFormat:@"news-content-%d", i];
        [self.newsData addObject:news];
    }
}

#pragma mark - Table view data source
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.newsData.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"NewsCell" forIndexPath:indexPath];
    
    LLNews *news = self.newsData[indexPath.row];
    
    cell.detailTextLabel.text = news.title;
    cell.textLabel.text = news.content;
    
    return cell;
}

#pragma mark - UITableViewDelegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"1111");
}

@end

優點：tableView和newsData都是相對獨立的，可以復用
缺點：大量的賦值代碼會寫在Controller中，Controller變得過于臃腫

變種的MVC

變種后的MVC的資料流向，Controller和View還是相互作用的，Controller也還是會去獲取資料來作為Model；不同的是View也可以直接持有Model了，三者之間互相都有了互動

-w502

下面我們用示例代碼來說明三者之間的具體關系

// LLApp
@interface LLApp : NSObject
@property (copy, nonatomic) NSString *name;
@property (copy, nonatomic) NSString *image;
@end

@implementation LLApp

@end

// LLAppView
@class LLApp, LLAppView;

@protocol LLAppViewDelegate <NSObject>
@optional
- (void)appViewDidClick:(LLAppView *)appView;
@end

@interface LLAppView : UIView
@property (strong, nonatomic) LLApp *app;
@property (weak, nonatomic) id<LLAppViewDelegate> delegate;
@end

@interface LLAppView()
@property (weak, nonatomic) UIImageView *iconView;
@property (weak, nonatomic) UILabel *nameLabel;
@end

@implementation LLAppView

- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        UIImageView *iconView = [[UIImageView alloc] init];
        iconView.frame = CGRectMake(0, 0, 100, 100);
        [self addSubview:iconView];
        _iconView = iconView;
        
        UILabel *nameLabel = [[UILabel alloc] init];
        nameLabel.frame = CGRectMake(0, 100, 100, 30);
        nameLabel.textAlignment = NSTextAlignmentCenter;
        [self addSubview:nameLabel];
        _nameLabel = nameLabel;
    }
    return self;
}

- (void)setApp:(LLApp *)app
{
    _app = app;
    
    self.iconView.image = [UIImage imageNamed:app.image];
    self.nameLabel.text = app.name;
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    if ([self.delegate respondsToSelector:@selector(appViewDidClick:)]) {
        [self.delegate appViewDidClick:self];
    }
}

@end

// ViewController
@interface ViewController () <LLAppViewDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 創建view
    LLAppView *appView = [[LLAppView alloc] init];
    appView.frame = CGRectMake(100, 100, 100, 150);
    appView.delegate = self;
    [self.view addSubview:appView];
    
    // 加載模型資料
    LLApp *app = [[LLApp alloc] init];
    app.name = @"QQ";
    app.image = @"QQ";
    
    // 設定資料到view上
    appView.app = app;
}

#pragma mark - LLAppViewDelegate
- (void)appViewDidClick:(LLAppView *)appView
{
    NSLog(@"控制器監聽到了appView的點擊");
}

@end

優點：Controller會相對減負，減少View的資料賦值代碼，而且外部不用關心View的屬性以及做了什么

缺點：View和Model耦合性太高了，會造成相互依賴，不能再分別單獨使用了，復用性降低了

MVP

MVP架構是以Model、Presenter、View三者之間的關系來依賴的

Presenter更像是替代了Controller來作為Model和View之間的橋梁，而Controller只需要管理Presenter就可以了

-w611

我們借由上面的示例來做下調整，示例代碼如下

LLApp和LLAppView基本不變

// LLApp
@interface LLApp : NSObject
@property (copy, nonatomic) NSString *name;
@property (copy, nonatomic) NSString *image;
@end

@implementation LLApp

@end

// LLAppView
@class LLAppView;

@protocol LLAppViewDelegate <NSObject>
@optional
- (void)appViewDidClick:(LLAppView *)appView;
@end

@interface LLAppView : UIView
- (void)setName:(NSString *)name andImage:(NSString *)image;
@property (weak, nonatomic) id<LLAppViewDelegate> delegate;
@end

@interface LLAppView()
@property (weak, nonatomic) UIImageView *iconView;
@property (weak, nonatomic) UILabel *nameLabel;
@end

@implementation LLAppView

- (instancetype)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {
        UIImageView *iconView = [[UIImageView alloc] init];
        iconView.frame = CGRectMake(0, 0, 100, 100);
        [self addSubview:iconView];
        _iconView = iconView;
        
        UILabel *nameLabel = [[UILabel alloc] init];
        nameLabel.frame = CGRectMake(0, 100, 100, 30);
        nameLabel.textAlignment = NSTextAlignmentCenter;
        [self addSubview:nameLabel];
        _nameLabel = nameLabel;
    }
    return self;
}

- (void)setName:(NSString *)name andImage:(NSString *)image
{
    _iconView.image = [UIImage imageNamed:image];
    _nameLabel.text = name;
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    if ([self.delegate respondsToSelector:@selector(appViewDidClick:)]) {
        [self.delegate appViewDidClick:self];
    }
}

@end

多出來的Presenter和抽取后的Controller代碼如下

// LLAppPresenter
@interface LLAppPresenter : NSObject

- (instancetype)initWithController:(UIViewController *)controller;
@end

@interface LLAppPresenter() <LLAppViewDelegate>

@property (weak, nonatomic) UIViewController *controller;
@end

@implementation LLAppPresenter

- (instancetype)initWithController:(UIViewController *)controller
{
    if (self = [super init]) {
        self.controller = controller;
        
        // 創建View
        LLAppView *appView = [[LLAppView alloc] init];
        appView.frame = CGRectMake(100, 100, 100, 150);
        appView.delegate = self;
        [controller.view addSubview:appView];
        
        // 加載模型資料
        LLApp *app = [[LLApp alloc] init];
        app.name = @"QQ";
        app.image = @"QQ";
        
        // 賦值資料
        [appView setName:app.name andImage:app.image];
    }
    return self;
}

#pragma mark - MJAppViewDelegate
- (void)appViewDidClick:(LLAppView *)appView
{
    NSLog(@"presenter 監聽了 appView 的點擊");
}

@end

// ViewController
@interface ViewController ()

@property (strong, nonatomic) LLAppPresenter *presenter;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.presenter = [[LLAppPresenter alloc] initWithController:self];
}

@end

優點：

每個Presenter對應著各自的Model和View
Model和View也更加的獨立性、可復用
Controller里變得更簡潔，只需要管理不同的Presenter就可以

MVVM

MVVM架構是以Model、ViewModel、View三者之間的關系來依賴的，其中的View包括了View和Controller

ViewModel的作用是將Controller的業務邏輯抽取出來，并且把Model和View做一個系結關系

-w693

我們將MVC的tableview的示例做了更改后，代碼如下

// LLNews
@interface LLNews : NSObject
@property (copy, nonatomic) NSString *title;
@property (copy, nonatomic) NSString *content;
@end

@implementation LLNews

@end

// LLNewsViewModel
@interface LLNewsViewModel : NSObject

- (void)loadNewsData:(void (^)(NSArray *newsData))completion;
@end

@implementation LLNewsViewModel

- (void)loadNewsData:(void (^)(NSArray *))completion
{
    if (!completion) return;
    
    NSMutableArray *newsData = https://www.cnblogs.com/funkyRay/p/[NSMutableArray array];
    for (int i = 0; i < 20; i++) {
        // 發送網路請求、字典轉模型
        LLNews *news = [[LLNews alloc] init];
        news.title = [NSString stringWithFormat:@"news-title-%d", i];
        news.content = [NSString stringWithFormat:@"news-content-%d", i];
        [newsData addObject:news];
    }
    
    completion(newsData);
}

@end

// LLNewsViewController
@interface LLNewsViewController ()
@property (nonatomic, strong) LLNewsViewModel *newsVM;
@property (nonatomic, assign) NSArray *newsData;
@end

@implementation LLNewsViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.newsVM = [[LLNewsViewModel alloc] init];
    [self.newsVM loadNewsData:^(NSArray *newsData) {
        self.newsData = https://www.cnblogs.com/funkyRay/p/newsData;
    }];
}

#pragma mark - Table view data source
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.newsData.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"NewsCell" forIndexPath:indexPath];
    
    LLNews *news = self.newsData[indexPath.row];
    
    cell.detailTextLabel.text = news.title;
    cell.textLabel.text = news.content;
    
    return cell;
}

#pragma mark - UITableViewDelegate
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSLog(@"1111");
}

@end

優點：Controller可以不用寫邏輯代碼，相對減輕負擔，MVVM可以結合一些回應式框架來更簡便使用

架構分層

一般我們經常會分為三層架構，分別是界面層、業務層、資料層

MVC、MVP、MVVM這幾種架構都是建立于界面層來討論的

架構分層的目的就是為了降低耦合性，易于維護和開發

設計模式

什么是設計模式

設計模式（Design Pattern）是一套被反復使用、代碼設計經驗的總結
使用設計模式的好處是：可重用代碼、讓代碼更容易被他人理解、保證代碼可靠性
一般與編程語言無關，是一套比較成熟的編程思想### 設計模式的幾大類設計模式可以分為三大類- 創建型模式：物件實體化的模式，用于解耦物件的實體化程序 - 單例模式、工廠方法模式，等等- 結構型模式：把類或物件結合在一起形成一個更大的結構 - 代理模式、配接器模式、組合模式、裝飾模式，等等- 行為型模式：類或物件之間如何互動，及劃分責任和演算法 - 觀察者模式、命令模式、責任鏈模式，等等具體概述之后再詳細討論

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