iOS底层原理--035：架构模式

1. MVC架构

MVC属于苹果推荐的架构模式，包含几个明显的特征：

• Model：模型层，封装了应用程序的数据，并定义操控和处理该数据的逻辑和运算

• View：视图层，用于视图控件的渲染，并且对用户的操作作出响应

• Controller：程序的视图对象和模型对象之间的交互和通讯，由控制器充当媒介，负责二者的执行设置和协调任务，并管理它们的生命周期

这种方式在实际开发中，会产生两个常见的问题：

• Controller中存在大量的代理、逻辑、UI和内部方法，导致VC层过重

• View和Model之间很容易产生依赖，导致耦合度过高

开发中，非常典型的View和Model产生依赖的代码：

一个好的架构，应该做到高内聚，低耦合。让代码的复用性提高，模块之间的依赖程度降低。简单来说，应该谁的事情谁做，模块之间各负其职，持续保持项目的生命周期

2. 轻量化VC

VC的实际意义，只是建立模块之间的依赖关系。但开发中，我们在VC中还会加入一些繁重的UI代码、啰嗦的业务逻辑、很长的网络层代码、难受的代理功能

这些原本不属于VC的业务代码，全部堆积在VC中，导致VC愈发笨重，难以维护

构建轻量级VC，把不属于VC的业务代码全部分散。例如：将常见的UITableView相关代理，使用自定义DataSource进行封装。将繁重的UI代码，使用自定义View进行封装

自定义DataSource封装UITableView相关代理，这个类对整个项目来说都可以被复用

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
typedef void (^CellConfigureBefore)(id cell, id model, NSIndexPath * indexPath);
@interface LMDataSource : NSObject<UITableViewDataSource,UICollectionViewDataSource>
@property (nonatomic, weak)  NSArray *dataArray;
- (id)initWithIdentifier:(NSString *)identifier configureBlock:(CellConfigureBefore)before;
@property (nonatomic, strong) IBInspectable NSString *cellIdentifier;
@property (nonatomic, copy) CellConfigureBefore cellConfigureBefore;
- (id)modelsAtIndexPath:(NSIndexPath *)indexPath;
@end
@implementation LMDataSource
- (id)initWithIdentifier:(NSString *)identifier configureBlock:(CellConfigureBefore)before {
    if(self = [super init]) {
        _cellIdentifier = identifier;
        _cellConfigureBefore = [before copy];
    }
    return self;
}
- (id)modelsAtIndexPath:(NSIndexPath *)indexPath {
    return self.dataArray.count > indexPath.row ? self.dataArray[indexPath.row] : nil;
}
#pragma mark UITableViewDataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return !self.dataArray  ? 0: self.dataArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:self.cellIdentifier forIndexPath:indexPath];
    id model = [self modelsAtIndexPath:indexPath];
    if(self.cellConfigureBefore) {
        self.cellConfigureBefore(cell, model,indexPath);
    }
    return cell;
}
#pragma mark UICollectionViewDataSource
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return !self.dataArray  ? 0: self.dataArray.count;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:self.cellIdentifier forIndexPath:indexPath];
    id model = [self modelsAtIndexPath:indexPath];
    if(self.cellConfigureBefore) {
        self.cellConfigureBefore(cell, model,indexPath);
    }
    return cell;
}
- (NSMutableArray *)dataArray{
    if (!_dataArray) {
        _dataArray = [NSMutableArray arrayWithCapacity:5];
    }
    return _dataArray;
}
@end

自定义View封装繁重的UI代码

#import <UIKit/UIKit.h>
#import "MVCTableViewCell.h"
@interface LGView : UIView
@property (nonatomic, strong) UITableView       *tableView;
- (void)setDataSource:(id<UITableViewDataSource>)dataSource;
@end
@implementation LGView
- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self addSubview:self.tableView];
    }
    return self;
}
- (void)setDataSource:(id<UITableViewDataSource>)dataSource{
    self.tableView.dataSource = dataSource;
}
- (UITableView *)tableView{
    if (!_tableView) {
        _tableView = [[UITableView alloc] initWithFrame:self.frame style:UITableViewStylePlain];
        _tableView.tableFooterView = [UIView new];
        _tableView.backgroundColor = [UIColor whiteColor];
        [_tableView registerClass:[MVCTableViewCell class] forCellReuseIdentifier:[MVCTableViewCell reuserId]];
    }
    return _tableView;
}
@end

轻量级VC中的代码

#import "MVCViewController.h"
#import "LMDataSource.h"
#import "MVCTableViewCell.h"
#import "Present.h"
#import "Model.h"
#import "LGView.h"
@interface MVCViewController ()
@property (nonatomic, strong) LGView            *lgView;
@property (nonatomic, strong) LMDataSource      *dataSource;
@property (nonatomic, strong) Present           *pt;
@end
@implementation MVCViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // 建立关系
    self.view = self.lgView;
    [self.dataSource setDataArray:self.pt.dataArray];
    [self.lgView setDataSource:self.dataSource];
}
#pragma mark - lazy
// UI布局代码
- (LGView *)lgView{
    if(!_lgView){
        _lgView = [[LGView alloc] initWithFrame:self.view.bounds];
    }
    return _lgView;
}
// 数据提供层
- (Present *)pt{
    if(!_pt){
        _pt = [[Present alloc] init];
    }
    return _pt;
}
// 数据代理层
- (LMDataSource *)dataSource{
    if(!_dataSource){
        _dataSource = [[LMDataSource alloc] initWithIdentifier:[MVCTableViewCell reuserId] configureBlock:^(MVCTableViewCell *cell, Model *model, NSIndexPath *indexPath) {
            cell.model = model;
        }];
    }
    return _dataSource;
}
@end

3. MVP架构

上述案例中，还存在UI与Model之间的强依赖关系

在Cell中，UI的展示需要使用Model

- (void)setModel:(Model *)model{
    _model              = model;
    self.numLabel.text  = model.num;
    self.nameLabel.text = model.name;
}

当用户点击Cell上的某个按钮发生交互，同样需要修改Model

- (void)didClickAddBtn:(UIButton *)sender{
    self.num++;
}
- (void)setNum:(int)num{
    _num                = num;
    self.numLabel.text  = [NSString stringWithFormat:@"%d",self.num];
    self.model.num      = self.numLabel.text;
}

对于UI和Model层的解耦处理，可以采用MVP面向协议编程，即Model View Presenter（模型 视图 协调器）

3.1 特征

• 任务均摊：将最主要的任务划分到Presenter和Model，而View的功能较少

• 可测试性：由于一个功能简单的View层，所以测试数业务逻辑变得简单

• 易用性：比使用MVC模式的代码量更多，但MVP模式具备非常清晰的结构

所以，MVC与MVP的区别就是，在MVP中Model和View没有直接通信

3.2 设计模式

• Model层不仅仅是创建一个数据对象，还应该包含网络请求，以及数据Cache的操作

• View层就是一些封装、重用

• Presenter层并不涉及数据的网络请求和Cache操作，只是搭建Model层和View层的一个桥梁

3.3 优势

• 模型与视图完全分离，修改视图而不影响模型

• 可以更高效地使用模型，因为所有交互都在Presenter中

• 把逻辑放在Presenter中，可以脱离用户接口进行单元测试

• 可以将一个Presener用于多个视图，而不需要改变Presenter的逻辑。这个特性非常的有用，因为视图的变化总是比模型的变化频繁

3.4 UI与Model解耦

创建LGProtocol，实现Cell中按钮点击的事件接口

#import <Foundation/Foundation.h>
@protocol LGProtocol <NSObject>
- (void)didClickNum:(NSString *)num indexpath:(NSIndexPath *)indexpath;
@end

在Present中，实现LGProtocol协议的didClickNum方法

#import <Foundation/Foundation.h>
#import "Model.h"
#import "LGProtocol.h"
#import <YYKit.h>
@interface Present : NSObject<LGProtocol>
@property (nonatomic, strong) NSMutableArray    *dataArray;
@property (nonatomic, weak) id<LGProtocol>       delegate;
@end
@implementation Present
- (instancetype)init{
    if (self = [super init]) {
        [self loadData];
    }
    return self;
}
- (void)loadData{
    NSArray *temArray =
    @[
      @{@"name":@"HK",@"imageUrl":@"http://HK",@"num":@"99"},
      @{@"name":@"KD",@"imageUrl":@"http://KD",@"num":@"99"},
      @{@"name":@"CC",@"imageUrl":@"http://CC",@"num":@"99"},
      @{@"name":@"KC",@"imageUrl":@"http://KC",@"num":@"59"},
      @{@"name":@"LA",@"imageUrl":@"http://LA",@"num":@"24"}];
    for (int i = 0; i<temArray.count; i++) {
        Model *m = [Model modelWithDictionary:temArray[i]];
        [self.dataArray addObject:m];
    }
}
#pragma mark -LGProtocol
- (void)didClickNum:(NSString *)num indexpath:(NSIndexPath *)indexpath{
    @synchronized (self) {
        if (indexpath.row < self.dataArray.count) {
            Model *model = self.dataArray[indexpath.row];
            model.num    = num;
        }
    }
}
#pragma mark - lazy
- (NSMutableArray *)dataArray{
    if (!_dataArray) {
        _dataArray = [NSMutableArray arrayWithCapacity:10];
    }
    return _dataArray;
}
@end

在MVCTableViewCell中，删除UI对Model的数据绑定。在按钮点击的交互方法中，调用delegate的didClickNum方法

- (void)didClickAddBtn:(UIButton *)sender{
    self.num++;
}
- (void)setNum:(int)num{
    _num                = num;
    self.numLabel.text  = [NSString stringWithFormat:@"%d",self.num];
    // 发出响应 model delegate UI 
    if (self.delegate && [self.delegate respondsToSelector:@selector(didClickNum:indexpath:)]) {
        [self.delegate didClickNum:self.numLabel.text indexpath:self.indexPath];
    }
}
// 删除UI对Model的数据绑定
//- (void)setModel:(Model *)model{
//    _model              = model;
//    self.numLabel.text  = model.num;
//    self.nameLabel.text = model.name;
//}

来到VC代码中LMDataSource的Block，完成Cell中UI对Model的数据绑定，以及delegate和indexPath的设置

#import "MVCViewController.h"
#import "LMDataSource.h"
#import "MVCTableViewCell.h"
#import "Present.h"
#import "Model.h"
#import "LGView.h"
@interface MVCViewController ()
@property (nonatomic, strong) LGView            *lgView;
@property (nonatomic, strong) LMDataSource      *dataSource;
@property (nonatomic, strong) Present           *pt;
@end
@implementation MVCViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // 建立关系
    self.view = self.lgView;
    [self.dataSource setDataArray:self.pt.dataArray];
    [self.lgView setDataSource:self.dataSource];
}
#pragma mark - lazy
// UI布局代码
- (LGView *)lgView{
    if(!_lgView){
        _lgView = [[LGView alloc] initWithFrame:self.view.bounds];
    }
    return _lgView;
}
// 数据提供层
- (Present *)pt{
    if(!_pt){
        _pt = [[Present alloc] init];
    }
    return _pt;
}
// 数据代理层
- (LMDataSource *)dataSource{
    if(!_dataSource){
        __weak typeof(self) weakSelf = self;
        _dataSource = [[LMDataSource alloc] initWithIdentifier:[MVCTableViewCell reuserId] configureBlock:^(MVCTableViewCell *cell, Model *model, NSIndexPath *indexPath) {
            __strong __typeof(weakSelf)strongSelf = weakSelf;
            cell.numLabel.text  = model.num;
            cell.nameLabel.text = model.name;
            cell.delegate       = strongSelf.pt;
            cell.indexPath      = indexPath;
        }];
    }
    return _dataSource;
}
@end

3.5 双向绑定

开发中遇到以下需求时，需要UI和Model进行双向绑定。例如：触发Cell的didClickAddBtn事件，当num++大于5，UI层只展示前两条数据

修改LGProtocol，增加UI刷新的事件接口

#import <Foundation/Foundation.h>
@protocol LGProtocol <NSObject>
- (void)didClickNum:(NSString *)num indexpath:(NSIndexPath *)indexpath;
- (void)reloadUI;
@end

修改Present中的didClickNum方法，增加num大于5，只保留前两条数据，并调用delegate的reloadUI方法刷新UI

- (void)didClickNum:(NSString *)num indexpath:(NSIndexPath *)indexpath{
    @synchronized (self) {
        if (indexpath.row < self.dataArray.count) {
            Model *model = self.dataArray[indexpath.row];
            model.num    = num;
            if ([num intValue] > 5) {
                [self.dataArray removeAllObjects];
                NSArray *temArray =
                @[
                  @{@"name":@"HK",@"imageUrl":@"http://HK",@"num":@"99"},
                  @{@"name":@"KC",@"imageUrl":@"http://KC",@"num":@"99"}];
                for (int i = 0; i<temArray.count; i++) {
                    Model *m = [Model modelWithDictionary:temArray[i]];
                    [self.dataArray addObject:m];
                }
                if (self.delegate && [self.delegate respondsToSelector:@selector(reloadUI)]) {
                    [self.delegate reloadUI];
                }
            }
        }
    }
}

修改LGView，实现LGProtocol协议的刷新UI方法

#import <UIKit/UIKit.h>
#import "MVCTableViewCell.h"
#import "LGProtocol.h"
@interface LGView : UIView<LGProtocol>
@property (nonatomic, strong) UITableView       *tableView;
- (void)setDataSource:(id<UITableViewDataSource>)dataSource;
@end
@implementation LGView
- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self addSubview:self.tableView];
    }
    return self;
}
- (void)setDataSource:(id<UITableViewDataSource>)dataSource{
    self.tableView.dataSource = dataSource;
}
- (void)reloadUI{
    [self.tableView reloadData];
}
- (UITableView *)tableView{
    if (!_tableView) {
        _tableView = [[UITableView alloc] initWithFrame:self.frame style:UITableViewStylePlain];
        _tableView.tableFooterView = [UIView new];
        _tableView.backgroundColor = [UIColor whiteColor];
        [_tableView registerClass:[MVCTableViewCell class] forCellReuseIdentifier:[MVCTableViewCell reuserId]];
    }
    return _tableView;
}
@end

修改MVCViewController，将UI和Model建立关系

- (void)viewDidLoad {
    [super viewDidLoad];
    // 建立关系
    self.view = self.lgView;
    [self.dataSource setDataArray:self.pt.dataArray];
    [self.lgView setDataSource:self.dataSource];
    //将UI和Model建立关系
    self.pt.delegate = self.lgView;
}

3.6 案例总结

对于上述MVP的简单案例，其实还存在很多缺陷。这种简陋的代码，连开发中常见的需求都难以满足

例如以下一些情况：

• 遇到更复杂的Cell形态

• 使用过多的delegate等胶水代码

• 当遇到模块层次更深的情况，相互之间难以通讯

所以，针对上述的问题，还要介绍一下MVP的真正使用方式

4. 适配器设计

当一个列表中出现多种Cell形态，可以使用适配器设计方式

创建KCBaseAdapter基类，基于UITableView的代理，实现基础方法

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@protocol KCBaseAdapterDelegate <NSObject>
@optional
- (void)didSelectCellData:(id)cellData;
- (void)deleteCellData:(id)cellData;
- (void)willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath;
@end
@protocol KCBaseAdapterScrollDelegate <NSObject>
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView ;
- (void)scrollViewDidScroll:(UIScrollView *)scrollView ;
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView;
@end
@protocol KCBaseAdapterPullUpDelegate <NSObject>
- (void)beginToRefresh;
@end
@interface KCBaseAdapter : NSObject<UITableViewDataSource, UITableViewDelegate>
{
}
@property (nonatomic, weak) id<KCBaseAdapterDelegate>   adapterDelegate;
@property (nonatomic, weak) id<KCBaseAdapterScrollDelegate>              adapterScrollDelegate;
@property (nonatomic, weak) id<KCBaseAdapterPullUpDelegate>              adapterPullUpDelegate;
@property (nonatomic, strong) NSMutableArray    *arr;
- (float)getTableContentHeight;
- (void)refreshCellByData:(id)data tableView:(UITableView*)tableView;
- (NSArray*)getAdapterArray;
- (void)setAdapterArray:(NSArray*)arr;
@end
@implementation KCBaseAdapter
- (instancetype)init
{
    self = [super init];
    if (self) {
        _arr = [NSMutableArray new];
    }
    return self;
}
- (NSArray*)getAdapterArray
{
    return _arr;
}
- (void)setAdapterArray:(NSArray*)arr
{
    [_arr removeAllObjects];
    [_arr addObjectsFromArray:arr];
}
- (float)getTableContentHeight
{
    return 0;
}
#pragma mark - 抽象方法
- (void)refreshCellByData:(id)data tableView:(UITableView*)tableView
{
}
#pragma mark    UITableView DataSource
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _arr.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row > self.getAdapterArray.count-1) {
        return [UITableViewCell new];
    }
    id cellData = [self.arr objectAtIndex:indexPath.row];
    UITableViewCell* cell = NULL;
    CCSuppressPerformSelectorLeakWarning(
                                         cell = [self performSelector:NSSelectorFromString([NSString stringWithFormat:@"tableView:cellFor%@:", [cellData class]]) withObject:tableView withObject:cellData];);
    return cell;
}
#pragma mark - UITableView Delegate
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 0;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row > self.getAdapterArray.count-1) {
        return;
    }
    [tableView deselectRowAtIndexPath:indexPath animated:false];
    id cellData = [self.arr objectAtIndex:indexPath.row];
    if (self.adapterDelegate) {
        if ([_adapterDelegate respondsToSelector:@selector(didSelectCellData:)]) {
            [_adapterDelegate didSelectCellData:cellData];
        }
    }
}
- (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row > self.getAdapterArray.count-1) {
        return;
    }
    if (self.adapterPullUpDelegate && [self.adapterPullUpDelegate respondsToSelector:@selector(beginToRefresh)]) {
        //倒数第三个 发送请求
        if (tableView.style == UITableViewStyleGrouped) {
            if (self.getAdapterArray.count >1) {
                NSArray *dataArray = [self.getAdapterArray objectAtIndex:0];
                if (dataArray.count > 4 && dataArray.count - 4 == indexPath.row) {
                    [self.adapterPullUpDelegate beginToRefresh];
                }
            }
        }
        else if (tableView.style == UITableViewStylePlain)
        {
            if (self.getAdapterArray.count > 4 && self.getAdapterArray.count - 4 == indexPath.row) {
                [self.adapterPullUpDelegate beginToRefresh];
            }
        }
    }
    if (self.adapterDelegate) {
        if ([_adapterDelegate respondsToSelector:@selector(willDisplayCell:forRowAtIndexPath:)]) {
            [_adapterDelegate willDisplayCell:cell forRowAtIndexPath:indexPath];
        }
    }
}
#pragma mark - UIScrollViewDelegate
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    if (self.adapterScrollDelegate && [self.adapterScrollDelegate respondsToSelector:@selector(scrollViewWillBeginDragging:)]) {
        [self.adapterScrollDelegate scrollViewWillBeginDragging:scrollView];
    }
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if (self.adapterScrollDelegate && [self.adapterScrollDelegate respondsToSelector:@selector(scrollViewDidScroll:)]) {
        [self.adapterScrollDelegate scrollViewDidScroll:scrollView];
    }
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    if (self.adapterScrollDelegate && [self.adapterScrollDelegate respondsToSelector:@selector(scrollViewDidEndDragging:)]) {
        [self.adapterScrollDelegate scrollViewDidEndDragging:scrollView];
    }
}
@end

创建KCHomeAdapter，继承于KCBaseAdapter，实现针对首页的业务逻辑

#import "KCHomeAdapter.h"
#import "KCHomeTableViewCell.h"
#import "KCChannelProfile.h"
@implementation KCHomeAdapter
- (CGFloat)getCellHeight:(NSInteger)row
{
    CGFloat height = SCREEN_WIDTH*608/1080 + 54;
    KCChannelProfile *model = [self.getAdapterArray objectAtIndex:row];
    if (model.title.length > 0) {
        CGSize titleSize = [model.title sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14]}];
        if (titleSize.width > SCREEN_WIDTH - 35) {
            // 两行
            height +=67;
        }else{
            height +=50;
        }
    }else{
        height += 8;
    }
    return height;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    return [self getCellHeight:indexPath.row];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.getAdapterArray.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    KCChannelProfile* liveModel = self.getAdapterArray[indexPath.row];
    UITableViewCell *cell = nil;
    CCSuppressPerformSelectorLeakWarning (
                                          cell = [self performSelector:NSSelectorFromString([NSString stringWithFormat:@"tableView:cellForKCChannelProfile:"]) withObject:tableView withObject:liveModel];
                                          );
    return cell;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForKCChannelProfile:(id)model {
    NSString *cellIdentifier = NSStringFromSelector(_cmd);
    KCHomeTableViewCell *cell = (KCHomeTableViewCell *)[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if (!cell) {
        cell = [[KCHomeTableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
    }
    KCChannelProfile* liveModel = model;
    [cell setCellContent:liveModel];
    return cell;
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:NO];
    id model = self.getAdapterArray[indexPath.row];
    if (self.adapterDelegate && [self.adapterDelegate respondsToSelector:@selector(didSelectCellData:)]) {
        [self.adapterDelegate didSelectCellData:model];
    }
}
@end

因为在项目中，针对不同业务的实现代码逻辑各不相同。我们在基类中只实现基础代码，通过继承或分类的形式，完成业务代码，以此方式做到去中心化，增强代码的复用性

5. context设计

创建宏定义，实现代理方法的万能调用

#define KC(instance, protocol, message) [(id<protocol>)(instance) message]

创建KCBaseViewController作为VC层的基类，内部实现UI层和Model层都依赖的Context上下文

#import "KCBaseViewController.h"
@interface KCBaseViewController ()
@property (nonatomic, strong) NSMutableDictionary   *eventMap;
@property (nonatomic, assign) BOOL                  mvpEnabled;
@end
@implementation KCBaseViewController
- (void)configMVP:(NSString*)name
{
    self.mvpEnabled = true;
    self.rootContext = [[CDDContext alloc] init]; //strong
    self.context = self.rootContext; //weak
    //presentor
    Class presenterClass = NSClassFromString([NSString stringWithFormat:@"KC%@Presenter", name]);
    if (presenterClass != NULL) { // 缓存
        self.context.presenter = [presenterClass new];
        self.context.presenter.context = self.context;
    }
    //interactor
    Class interactorClass = NSClassFromString([NSString stringWithFormat:@"KC%@Interactor", name]);
    if (interactorClass != NULL) {
        self.context.interactor = [interactorClass new];
        self.context.interactor.context = self.context;
    }
    //view
    Class viewClass = NSClassFromString([NSString stringWithFormat:@"KC%@View", name]);
    if (viewClass != NULL) {
        self.context.view = [viewClass new];
        self.context.view.context = self.context;
    }
    //build relation
    self.context.presenter.view = self.context.view;
    self.context.presenter.baseController = self;
    self.context.interactor.baseController = self;
    self.context.view.presenter = self.context.presenter;
    self.context.view.interactor = self.context.interactor;
}
- (void)viewDidLoad
{
    [super viewDidLoad];
    if (self.mvpEnabled) {
        self.context.view.frame = self.view.bounds;
        self.view = self.context.view;
    }
    KCLog(@"\n\nDid Load ViewController: %@\n\n", [self class]);
}
- (void)dealloc
{
    KCLog(@"\n\nReleasing ViewController: %@\n\n", [self class]);
    [Notif removeObserver:self];
}
@end

• VC下的context为rootContext
• rootContext下包含presenter、interactor、view的创建，并对各层级下的context进行赋值
• 文件的命名，必须和代码规则一致

找到CDDContext、CDDPresenter、CDDInteractor、CDDView的定义：

#import <Foundation/Foundation.h>
#import "NSObject+CDD.h"
@class CDDContext;
@class CDDView;
@interface CDDPresenter : NSObject
@property (nonatomic, weak) UIViewController*           baseController;
@property (nonatomic, weak) CDDView*                    view;
@property (nonatomic, weak) id                          adapter; //for tableview adapter
@end
@interface CDDInteractor : NSObject
@property (nonatomic, weak) UIViewController*           baseController;
@end
@interface CDDView : UIView
@property (nonatomic, weak) CDDPresenter*               presenter;
@property (nonatomic, weak) CDDInteractor*              interactor;
@end
//Context bridges everything automatically, no need to pass it around manually
@interface CDDContext : NSObject
@property (nonatomic, strong) CDDPresenter*           presenter;
@property (nonatomic, strong) CDDInteractor*          interactor;
@property (nonatomic, strong) CDDView*                view; //view holds strong reference back to context
@end
@implementation CDDPresenter
@end
@implementation CDDInteractor
@end
@implementation CDDView
- (void)dealloc
{
    self.context = nil;
}
@end
@implementation CDDContext
- (void)dealloc
{
    NSLog(@"context being released");
}
@end

• 对于Context上下文，它只负责信息的综合管理，不负责业务细节的实现，所以并不存在臃肿的现象

6. context分发

无论自定义View的层级有多深，都可以调用到context上下文

例如：直播页面中弹出的礼物列表弹窗，点击发送礼物的事件

- (void)buttonSendClicked:(id)sender
{
    if (_selectedItem) {
        KC(self.context.presenter, KCLiveStreamPresenterDeleagte, sendGiftWithIndex:(int)_selectedItem.tag);
    }
}

子View中的context上下文的构建方式，通过VC层对context进行设置，而context实际上是基于NSObject创建的CDD分类，在分类中使用关联对象的方式进行设置

#import "NSObject+CDD.h"
#import "CDDContext.h"
#import <objc/runtime.h>
@implementation NSObject (CDD)
@dynamic context;
- (void)setContext:(CDDContext*)object {
    objc_setAssociatedObject(self, @selector(context), object, OBJC_ASSOCIATION_ASSIGN);
}
- (CDDContext*)context {
    id curContext = objc_getAssociatedObject(self, @selector(context));
    if (curContext == nil && [self isKindOfClass:[UIView class]]) {
        //try get from superview, lazy get
        UIView* view = (UIView*)self;
        UIView* sprView = view.superview;
        while (sprView != nil) {
            if (sprView.context != nil) {
                curContext = sprView.context;
                break;
            }
            sprView = sprView.superview;
        }
        if (curContext != nil) {
            [self setContext:curContext];
        }
    }
    return curContext;
}
+ (void)swizzleInstanceSelector:(SEL)oldSel withSelector:(SEL)newSel
{
    Method oldMethod = class_getInstanceMethod(self, oldSel);
    Method newMethod = class_getInstanceMethod(self, newSel);
    if (!oldMethod || !newMethod)
    {
        return;
    }
    class_addMethod(self,
                    oldSel,
                    class_getMethodImplementation(self, oldSel),
                    method_getTypeEncoding(oldMethod));
    class_addMethod(self,
                    newSel,
                    class_getMethodImplementation(self, newSel),
                    method_getTypeEncoding(newMethod));
    method_exchangeImplementations(class_getInstanceMethod(self, oldSel),
                                   class_getInstanceMethod(self, newSel));
}
@end

如果当前对象为UIView的实例对象，并且context上下文不存在，会遍历当前对象的父容器，找到可用的context，并对当前对象的context进行赋值

这样就保证了在VC下的所有子View，都能找到可用上下文，从而解决模块之间的通讯问题

总结

MVC架构：

• 设计模式

  • Model：模型层，封装了应用程序的数据，并定义操控和处理该数据的逻辑和运算

  • View：视图层，用于视图控件的渲染，并且对用户的操作作出响应

  • Controller：程序的视图对象和模型对象之间的交互和通讯，由控制器充当媒介，负责二者的执行设置和协调任务，并管理它们的生命周期

• 常见问题

  • Controller中存在大量的代理、逻辑、UI和内部方法，导致VC层过重

  • View和Model之间很容易产生依赖，导致耦合度过高

轻量化VC：

• VC的实际意义，只是建立模块之间的依赖关系

• 避免在VC中加入繁重的UI代码、啰嗦的业务逻辑、很长的网络层代码、难受的代理功能

MVP架构：

• 特征

  • 任务均摊：将最主要的任务划分到Presenter和Model，而View的功能较少

  • 可测试性：由于一个功能简单的View层，所以测试数业务逻辑变得简单

  • 易用性：比使用MVC模式的代码量更多，但MVP模式具备非常清晰的结构

• 设计模式

  • Model层不仅仅是创建一个数据对象，还应该包含网络请求，以及数据Cache的操作

  • View层就是一些封装、重用

  • Presenter层并不涉及数据的网络请求和Cache操作，只是搭建Model层和View层的一个桥梁

• 优势

  • 模型与视图完全分离，修改视图而不影响模型

  • 可以更高效地使用模型，因为所有交互都在Presenter中

  • 把逻辑放在Presenter中，可以脱离用户接口进行单元测试

  • 可以将一个Presener用于多个视图，而不需要改变Presenter的逻辑。这个特性非常的有用，因为视图的变化总是比模型的变化频繁