写给iOS小白的MVVM教程(一): 从MVC到MVVM之一个典型的MVC应用场景

前言

本着实践为主的原则,此系列文章不做过多的概念性的阐述和讨论;更多的代码和篇幅用来展示MVC和MVVC下的基础代码结构与具体实现,来展示各自优劣.这篇文章,更多的在于发掘MVC与MVVC的共性,以期为那些对MVVC感兴趣的iOS开发者,找到一种平滑的过渡与重构代码的方式.如果对MVVC感兴趣,可以直接将本文的大部分代码引用到自己的项目中,毕竟代码是写出来的!开篇之前,你可以先到这里下载本文的示例工程: https://github.com/ios122/ios122

在这一篇章里,我会分别使用我所理解的MVC与MVVC两种模式来完成同一个应用场景,以期帮助那些熟悉传统MVC模式代码的iOS攻城狮,能更好理解MVVC.限于篇幅,将MVC和MVVM拆分为两个部分,今天要说的是一个典型的MVC的应用场景,为基于MVC的MVVM重构做个基础.这篇文章着重进行了接口准备,必须的知识点的说明等内容.

预设场景:按分类请求一组博客,点击获取博客详情

我们选取最常见的一组场景: 根据某种规则获取一组数据,点击某一条数据,可以跳转到下一界面获取数据详情.这里我会根据分类请求此分类下的博客列表,点击某一条信息,可跳转到博客详情页.简单说,其实我们真正需要实现的只有两个页面: 博客分类列表页与博客详情页.

数据接口准备

我们至少需要两个接口,一个可以根据分类来获取博客列表,一个用来根据id获取博客详情.

使用预定义的接口

如果你没有自己的服务器或者对服务器开发不熟悉,可以使用我准备的这两个测试接口:

博客列表接口

http://www.ios122.com/find_php/index.php?viewController=YFPostListViewController&model[category]=ui&model[page]=2

ui 分类名称,目前预定义支持: ui, network, tool,autolayout 四个分类.
2,获取第几页的数据,从0开始计数,指请求此分类下第几页的数据.预定义每个分类下有100条数据,每20条数据一页.
返回示例:

[

    {

        "id": "ui_40",

        "title": "title_ui_40",

        "desc": "desc_ui_40"

    },

    {

        "id": "ui_41",

        "title": "title_ui_41",

        "desc": "desc_ui_41"

    },

    {

        "id": "ui_42",

        "title": "title_ui_42",

        "desc": "desc_ui_42"

    },

    {

        "id": "ui_43",

        "title": "title_ui_43",

        "desc": "desc_ui_43"

    },

    {

        "id": "ui_44",

        "title": "title_ui_44",

        "desc": "desc_ui_44"

    },

    {

        "id": "ui_45",

        "title": "title_ui_45",

        "desc": "desc_ui_45"

    },

    {

        "id": "ui_46",

        "title": "title_ui_46",

        "desc": "desc_ui_46"

    },

    {

        "id": "ui_47",

        "title": "title_ui_47",

        "desc": "desc_ui_47"

    },

    {

        "id": "ui_48",

        "title": "title_ui_48",

        "desc": "desc_ui_48"

    },

    {

        "id": "ui_49",

        "title": "title_ui_49",

        "desc": "desc_ui_49"

    },

    {

        "id": "ui_50",

        "title": "title_ui_50",

        "desc": "desc_ui_50"

    },

    {

        "id": "ui_51",

        "title": "title_ui_51",

        "desc": "desc_ui_51"

    },

    {

        "id": "ui_52",

        "title": "title_ui_52",

        "desc": "desc_ui_52"

    },

    {

        "id": "ui_53",

        "title": "title_ui_53",

        "desc": "desc_ui_53"

    },

    {

        "id": "ui_54",

        "title": "title_ui_54",

        "desc": "desc_ui_54"

    },

    {

        "id": "ui_55",

        "title": "title_ui_55",

        "desc": "desc_ui_55"

    },

    {

        "id": "ui_56",

        "title": "title_ui_56",

        "desc": "desc_ui_56"

    },

    {

        "id": "ui_57",

        "title": "title_ui_57",

        "desc": "desc_ui_57"

    },

    {

        "id": "ui_58",

        "title": "title_ui_58",

        "desc": "desc_ui_58"

    },

    {

        "id": "ui_59",

        "title": "title_ui_59",

        "desc": "desc_ui_59"

    }

]

2.博客详情接口

http://www.ios122.com/find_php/index.php?viewController=YFPostViewController&model[id]=ui_0

ui_0 表示博客唯一标识.其应为分类博客列表返回的一个有效id.
返回示例:

{

    "title": "title of ui_0",

    "body": "<h2>Hello iOS122</h2> Scann To Join Us <br /> <image alt=\"qq\" src=\"https://raw.githubusercontent.com/ios122/ios122/master/1443002712802.png\" />"

}

自定义接口

如果你有自己的服务器接口,直接使用即可;但是下面的oc代码,你可能也要对应变换下;如果你对服务器接口开发不是很了解,可以先阅读下这篇文章: iOS程序猿如何快速掌握 PHP,化身”全栈攻城狮”?.

假定,你已经阅读并领会了 << iOS程序猿如何快速掌握 PHP,化身”全栈攻城狮”? >>,这篇文章,新建问及那,并把下面的代码复制到对应文件中,然后根据自己的需要更改即可:

博客列表接口源文件

<?php // YFPostListViewController.php

class YFPostListViewController

{

  public $model = array(); //!< 传入的数据.

  private $countOfPerPage = 20; //!< 每页数据条数.

  /* 获取内容,用于输出显示. */

  protected function getContent()

  {

    /* 预定义一组数据 */

    $datasource = array();

    $categorys = array('ui', 'network', 'tool', 'autolayout');

    for ($i=0; $i < count($categorys); $i++) {

      $categoryName = $categorys[$i];

      $categoryData = array();

      for ($j=0; $j < 100; $j++) {

        $item = array(

          'id' => "{$categoryName}_{$j}",

          'title' => "title_{$categoryName}_{$j}",

          'desc' => "desc_{$categoryName}_{$j}"

        );

        $categoryData[$j] = $item;

      }

      $datasource[$categoryName] = $categoryData;

    }

    $queryCategoryName = $this->model['category'];

    $queryPage = $this->model['page'];

    $targetCategoryData = $datasource[$queryCategoryName];

    $content = array();

    for ($i = $this->countOfPerPage * $queryPage ; $i < $this->countOfPerPage * ($queryPage + 1); $i ++ ) {

      $content[] = $targetCategoryData[$i];

    }

    $content = json_encode($content);

     return $content;

  }

  public function show()

  {

   $content = $this->getContent();

   header("Content-type: application/json");

   echo $content;

  }

}

博客详情接口源文件

<?php // YFPostViewController.php

class YFPostViewController

{

  public $model = array(); //!< 传入的数据.

  /* 获取内容,用于输出显示. */

  protected function getContent()

  {

    $id = $this->model['id'];

    $content = array(

      'title' => "title of {$id}",

      'body' => '<h2>Hello iOS122</h2> Scann To Join Us <br /> <image alt="qq" src="https://raw.githubusercontent.com/ios122/ios122/master/1443002712802.png" />'

    );

    $content = json_encode($content);

     return $content;

  }

  public function show()

  {

   $content = $this->getContent();

   header("Content-type: application/json");

   echo $content;

  }

}

MVC 版本实现: 类似的代码,你不知道敲过了多少遍

技术要点

下面列出将要用到的技术点,如有你不熟悉的,可点击对应链接访问:

使用 AFNetworking 来处理网络请求;
使用 MJExtension实现JSON到数据模型的自动转换;
使用 MJRefresh 实现下拉刷新与上拉加载更多的效果;
使用 Masonry 进行AutoLayout布局;
使用 MBProgressHUD 优化页面加载时的进度提示;

思路分析

博客分类列表页面:
1. 在前一页面指定博客分类;
2. 页面加载时自动发起网络请求获取对应分类的数据;
3. 获取数据成功后,自动刷新视图;获取失败,则给出错误提示;
4. 点击某一条数据,可跳转到博客详情页.
博客详情页面:
1. 在前一页面指定博客id;
2. 页面加载时自动发起网络请求获取id的博客详情;
3. 获取成功后,自动刷新视图;获取失败,则给出错误提示.

博客列表页面

1. 在前一页面指定博客分类;

这一步,大家肯定都会:

YFMVCPostListViewController * mvcPostListVC = [[YFMVCPostListViewController alloc] init];

mvcPostListVC.categoryName = @"ui";

[self.navigationController pushViewController: mvcPostListVC animated: YES];

2. 页面加载时自动发起网络请求获取对应分类的数据;

为了保证每次都能进入列表页,都能自动刷新数据,建议在 viewWillAppear:方法刷新数据:

- (void)viewWillAppear:(BOOL)animated

{

    [super viewWillAppear: animated];

    [self updateData];

}

updateData方法进行数据的更新:

- (void)updateData

{

    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

    NSString * urlStr = [NSString stringWithFormat: @"http://www.ios122.com/find_php/index.php?viewController=YFPostListViewController&model[category]=%@&model[page]=0", self.categoryName];

    [manager GET: urlStr parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {

        NSLog(@"JSON: %@", responseObject);

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        NSLog(@"Error: %@", error);

    }];

}

此处使用的是预定义接口,数据请求成功后,控制台输入如下:

JSON: (

        {

        desc = "desc_ui_0";

        id = "ui_0";

        title = "title_ui_0";

    },

        {

        desc = "desc_ui_1";

        id = "ui_1";

        title = "title_ui_1";

    },

        {

        desc = "desc_ui_2";

        id = "ui_2";

        title = "title_ui_2";

    },

        {

        desc = "desc_ui_3";

        id = "ui_3";

        title = "title_ui_3";

    },

        {

        desc = "desc_ui_4";

        id = "ui_4";

        title = "title_ui_4";

    },

        {

        desc = "desc_ui_5";

        id = "ui_5";

        title = "title_ui_5";

    },

        {

        desc = "desc_ui_6";

        id = "ui_6";

        title = "title_ui_6";

    },

        {

        desc = "desc_ui_7";

        id = "ui_7";

        title = "title_ui_7";

    },

        {

        desc = "desc_ui_8";

        id = "ui_8";

        title = "title_ui_8";

    },

        {

        desc = "desc_ui_9";

        id = "ui_9";

        title = "title_ui_9";

    },

        {

        desc = "desc_ui_10";

        id = "ui_10";

        title = "title_ui_10";

    },

        {

        desc = "desc_ui_11";

        id = "ui_11";

        title = "title_ui_11";

    },

        {

        desc = "desc_ui_12";

        id = "ui_12";

        title = "title_ui_12";

    },

        {

        desc = "desc_ui_13";

        id = "ui_13";

        title = "title_ui_13";

    },

        {

        desc = "desc_ui_14";

        id = "ui_14";

        title = "title_ui_14";

    },

        {

        desc = "desc_ui_15";

        id = "ui_15";

        title = "title_ui_15";

    },

        {

        desc = "desc_ui_16";

        id = "ui_16";

        title = "title_ui_16";

    },

        {

        desc = "desc_ui_17";

        id = "ui_17";

        title = "title_ui_17";

    },

        {

        desc = "desc_ui_18";

        id = "ui_18";

        title = "title_ui_18";

    },

        {

        desc = "desc_ui_19";

        id = "ui_19";

        title = "title_ui_19";

    }

)

3. 获取数据成功后,自动刷新视图;获取失败,则给出错误提示;

这一部分,涉及的变动较多,我就直接贴代码了.你会注意到View和数据已经交叉进行了,很乱的感觉.而这也是我们想要使用MVVM重构代码的重要原因之一.

//

//  YFMVCPostListViewController.m

//  iOS122

//

//  Created by 颜风 on 15/10/14.

//  Copyright (c) 2015年 iOS122. All rights reserved.

//

#import "YFMVCPostListViewController.h"

#import "YFArticleModel.h"

#import <AFNetworking.h>

#import <MJRefresh.h>

#import <MBProgressHUD.h>

@interface YFMVCPostListViewController ()<UITableViewDelegate, UITableViewDataSource>

@property (nonatomic, strong) UITableView * tableView;

@property (nonatomic, strong) NSMutableArray * articles; //!< 文章数组,内部存储AFArticleModel类型.

@property (assign, nonatomic) NSInteger page; //!< 数据页数.表示下次请求第几页的数据.

@end

@implementation YFMVCPostListViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view.

}

- (NSMutableArray *)articles

{

    if (nil == _articles) {

        _articles = [NSMutableArray arrayWithCapacity: 42];

    }

    return _articles;

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

- (void)viewWillAppear:(BOOL)animated

{

    [super viewWillAppear: animated];

    // 马上进入刷新状态

    [self.tableView.header beginRefreshing];

}

- (UITableView *)tableView

{

    if (nil == _tableView) {

        _tableView = [[UITableView alloc] init];

        [self.view addSubview: _tableView];

        [_tableView makeConstraints:^(MASConstraintMaker *make) {

            make.edges.equalTo(UIEdgeInsetsMake(0, 0, 0, 0));

        }];

        _tableView.delegate = self;

        _tableView.dataSource = self;

        NSString * cellReuseIdentifier = NSStringFromClass([UITableViewCell class]);

        [_tableView registerClass: NSClassFromString(cellReuseIdentifier) forCellReuseIdentifier:cellReuseIdentifier];

        _tableView.header = [MJRefreshNormalHeader headerWithRefreshingBlock:^{

            self.page = 0;

            [self updateData];

        }];

        _tableView.footer = [MJRefreshBackNormalFooter footerWithRefreshingBlock:^{

            [self updateData];

        }];

    }

    return _tableView;

}

/**

 * 更新视图.

 */

- (void) updateView

{

    [self.tableView reloadData];

}

/**

 *  更新数据.

 *

 *  数据更新后,会自动更新视图.

 */

- (void)updateData

{

    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

    NSString * urlStr = [NSString stringWithFormat: @"http://www.ios122.com/find_php/index.php?viewController=YFPostListViewController&model[category]=%@&model[page]=%ld", self.categoryName, (long)self.page ++];

    [manager GET: urlStr parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {

        [self.tableView.header endRefreshing];

        [self.tableView.footer endRefreshing];

        if (1 == self.page) { // 说明是在重新请求数据.

            self.articles = nil;

        }

        NSArray * responseArticles = [YFArticleModel objectArrayWithKeyValuesArray: responseObject];

        [self.articles addObjectsFromArray: responseArticles];

        [self updateView];

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        [self.tableView.header endRefreshing];

        [self.tableView.footer endRefreshing];

        MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];

        hud.mode = MBProgressHUDModeText;

        hud.labelText = @"您的网络不给力!";

        [hud hide: YES afterDelay: 2];

    }];

}

# pragma mark - tabelView代理方法.

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section

{

    NSInteger number  = self.articles.count;

    return number;

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

    NSString * cellReuseIdentifier = NSStringFromClass([UITableViewCell class]);

    UITableViewCell * cell = [tableView dequeueReusableCellWithIdentifier: cellReuseIdentifier forIndexPath:indexPath];

    YFArticleModel * model = self.articles[indexPath.row];

    NSString * content = [NSString stringWithFormat: @"标题:%@ 内容:%@", model.title, model.desc];

    cell.textLabel.text = content;

    return cell;

}

@end

4. 点击某一条数据,可跳转到博客详情页.

只需要再额外实现下 -tableView: didSelectRowAtIndexPath:方法即可:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

{

    // 跳转到博客详情.

    YFArticleModel * articleModel = self.articles[indexPath.row];

    YFMVCPostViewController * postVC = [[YFMVCPostViewController alloc] init];

    postVC.articleID = articleModel.id;

    [self.navigationController pushViewController: postVC animated: YES];

}

博客详情页面

1. 在前一页面指定博客id;

这里其实就是博客列表的控制器的那几句:

// 跳转到博客详情.

YFArticleModel * articleModel = self.articles[indexPath.row];

YFMVCPostViewController * postVC = [[YFMVCPostViewController alloc] init];

postVC.articleID = articleModel.id;

[self.navigationController pushViewController: postVC animated: YES];

2. 页面加载时自动发起网络请求获取id的博客详情;

此处为了方便,我们依然使用预定义的博客详情接口:

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

    NSString * urlStr = [NSString stringWithFormat: @"http://www.ios122.com/find_php/index.php?viewController=YFPostViewController&model[id]=%@", self.articleID];

    [manager GET: urlStr parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {

        NSLog(@"%@", responseObject);

        [self updateView];

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];

        hud.mode = MBProgressHUDModeText;

        hud.labelText = @"您的网络不给力!";

        [hud hide: YES afterDelay: 2];

    }];

请求的输入,Xcode控制台打印输出,类似于:

{

    body = "<h2>Hello iOS122</h2> Scann To Join Us <br /> <image alt=\"qq\" src=\"https://raw.githubusercontent.com/ios122/ios122/master/1443002712802.png\" />";

    title = "title of ui_0";

}

3. 获取成功后,自动刷新视图;获取失败,则给出错误提示.

你会注意到,我们在上一步获取的数据,body部分内部是HTML字符串,所以我们要使用webView来显示博客详情.这和最近炒得很火的的混合开发模式有些像,但是目前主流的博客应用,几乎都是这么做的.完整代码如下:

//

//  YFMVCPostViewController.m

//  iOS122

//

//  Created by 颜风 on 15/10/16.

//  Copyright (c) 2015年 iOS122. All rights reserved.

//

#import "YFMVCPostViewController.h"

#import "YFArticleModel.h"

#import <AFNetworking.h>

#import <MBProgressHUD.h>

@interface YFMVCPostViewController ()<UIWebViewDelegate>

@property (strong, nonatomic) UIWebView * webView;

@property (strong, nonatomic) YFArticleModel * article;

@end

@implementation YFMVCPostViewController

- (UIWebView *)webView

{

    if (nil == _webView) {

        _webView = [[UIWebView alloc] init];

        [self.view addSubview: _webView];

        [_webView makeConstraints:^(MASConstraintMaker *make) {

            make.edges.equalTo(UIEdgeInsetsMake(64, 0, 0, 0));

        }];

    }

    return _webView;

}

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view.

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

- (void)viewWillAppear:(BOOL)animated

{

    [super viewWillAppear: animated];

    [self updateData];

}

/**

 * 更新视图.

 */

- (void) updateView

{

    [self.webView loadHTMLString: self.article.body baseURL:nil];

}

/**

 *  更新数据.

 *

 *  数据更新后,会自动更新视图.

 */

- (void)updateData

{

    [MBProgressHUD showHUDAddedTo:self.view animated: YES];

    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

    NSString * urlStr = [NSString stringWithFormat: @"http://www.ios122.com/find_php/index.php?viewController=YFPostViewController&model[id]=%@", self.articleID];

    [manager GET: urlStr parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {

        self.article = [YFArticleModel objectWithKeyValues: responseObject];

        [self updateView];

    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {

        MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];

        hud.mode = MBProgressHUDModeText;

        hud.labelText = @"您的网络不给力!";

        [hud hide: YES afterDelay: 2];

    }];

}

@end

小结

此篇主要展示了一个典型的列表-->详情场景的MVC实现,相关技术代码可以直接用于自己的项目中.尽管这是简化的场景,但依然可以很明显地看出来数据,网络请求与视图间的相互调用,使代码整体的可复用性大大降低! 而这,也是我们下次要用 MVVC 重构这个示例的核心目的之一!