iOS中的MVC和MVVM

MVC

MVC的实现思路是：用户操作View，在Controller层完成业务逻辑处理，更新Model层，将数据显示在View层。
在MVC中，每个层之间都有关联，耦合比较紧，在大型项目中，维护起来比较费力。
View把控制权交给Controller层，自己不执行业务逻辑；Controller层执行业务逻辑并且操作Model层，但不会直接操作View层；View和Model层的同步消息是通过观察者模式进行，而同步操作是由View层自己请求Model层的数据，然后对视图进行更新，观察者模式可以做到多视图同时更新。

MVC结构如图所示：

image.png

模型层：

Person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (nonatomic, readonly) NSString *firstName;
@property (nonatomic, readonly) NSString *lastName;

- (instancetype)initWithFirstName:(NSString *)firstName lastName:(NSString *)lastName;

@end

Person.m

#import "Person.h"

@implementation Person

- (instancetype)initWithFirstName:(NSString *)firstName lastName:(NSString *)lastName {
    self = [super init];
    if (self) {
        _firstName = firstName;
        _lastName = lastName;
    }
    return self;
}

@end

视图层：

TestView.h

#import <UIKit/UIKit.h>

@interface TestView : UIView

@property (nonatomic, strong) UILabel *nameLabel;

@end

TestView.m

#import "TestView.h"

@implementation TestView

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.nameLabel = [[UILabel alloc] initWithFrame:self.bounds];
        self.nameLabel.textAlignment = NSTextAlignmentCenter;
        [self addSubview:self.nameLabel];
    }
    return self;
}

@end

控制器层：

ViewController.m

#import "ViewController.h"
#import "Person.h"
#import "TestView.h"

@interface ViewController ()

@property (nonatomic, strong) Person *personModel;
@property (nonatomic, strong) TestView *testView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [self setupViews];

    if (self.personModel.firstName.length > 0) {
        self.testView.nameLabel.text = self.personModel.firstName;
    } else {
        self.testView.nameLabel.text = self.personModel.lastName;
    }

}

- (void)setupViews {
    self.personModel = [[Person alloc] initWithFirstName:@"" lastName:@"胡歌"];
    self.testView = [[TestView alloc] initWithFrame:CGRectMake(100, 100, CGRectGetWidth(self.view.bounds)-200, 50)];
    [self.view addSubview:self.testView];
}

@end

MVVM

MVVM和MVP的最大区别是采用了双向绑定机制，View的变动，自动反映在ViewModel上。
MVVM结构如图：

image.png

模型层：
Person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (nonatomic, readonly) NSString *firstName;
@property (nonatomic, readonly) NSString *lastName;

- (instancetype)initWithFirstName:(NSString *)firstName lastName:(NSString *)lastName;

@end

Person.m

#import "Person.h"

@implementation Person

- (instancetype)initWithFirstName:(NSString *)firstName lastName:(NSString *)lastName {
    self = [super init];
    if (self) {
        _firstName = firstName;
        _lastName = lastName;
    }
    return self;
}

@end

视图层：
TestView.h

#import <UIKit/UIKit.h>

@interface TestView : UIView

@property (nonatomic, strong) UILabel *nameLabel;

@end

TestView.m

#import "TestView.h"

@implementation TestView

- (instancetype)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.nameLabel = [[UILabel alloc] initWithFrame:self.bounds];
        self.nameLabel.textAlignment = NSTextAlignmentCenter;
        [self addSubview:self.nameLabel];
    }
    return self;
}

@end

ViewModel层：

PersonViewModel.h

#import <Foundation/Foundation.h>
#import "Person.h"

@interface PersonViewModel : NSObject

@property (nonatomic, readonly) Person *person;
@property (nonatomic, readonly) NSString *nameText;

- (instancetype)initWithPerson:(Person *)person;

@end

PersonViewModel.m

#import "PersonViewModel.h"

@implementation PersonViewModel

- (instancetype)initWithPerson:(Person *)person {
    self = [super init];
    if (self) {
        _person = person;
        if (_person.firstName.length > 0) {
            _nameText = _person.firstName;
        } else {
            _nameText = _person.lastName;
        }
    }
    return self;
}

@end

ViewController.m

#import "ViewController.h"
#import "PersonViewModel.h"
#import "TestView.h"

@interface ViewController ()

@property (nonatomic, strong) TestView *testView;
@property (nonatomic, strong) PersonViewModel *viewModel;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    [self setupViews];

    self.testView.nameLabel.text = self.viewModel.nameText;

}

- (void)setupViews {
    Person *person = [[Person alloc] initWithFirstName:@"" lastName:@"胡歌"];
    self.viewModel = [[PersonViewModel alloc] initWithPerson:person];
    self.testView = [[TestView alloc] initWithFrame:CGRectMake(100, 100, CGRectGetWidth(self.view.bounds)-200, 50)];
    [self.view addSubview:self.testView];
}

@end