第三方(SDWebImage, 网络类AFNetWorking)

    [self.myTableView registerClass:[UITableViewCell class] forCellReuseIdentifier:identifier];

当需要展示一个cell时, 就去重用池中找cell, 如果有, 就直接使用, 如果没有, 会根据之前注册的cell类型, 自动创建一个cell
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier forIndexPath:indexPath];
    cell.textLabel.text = @"Hello World";
    cell.detailTextLabel.text = @"你好, 世界!";
    return cell; 

    static NSString *identifier1 = @"MyCell";
    MyCell *myCell = [tableView dequeueReusableCellWithIdentifier:identifier1];
    if (myCell == nil) {
        //Xib编译过后就是Nib文件
        myCell = [[[NSBundle mainBundle] loadNibNamed:@"MyCell" owner:self options:nil] firstObject];
    }
    return myCell; 

    [self.myTableView registerNib:[UINib nibWithNibName:@"MyCell" bundle:nil] forCellReuseIdentifier:identifier2];

    MyCell *cell = [tableView dequeueReusableCellWithIdentifier:identifier2 forIndexPath:indexPath];
    return cell; 

     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"storyboard" forIndexPath:indexPath];
    return cell;

HometableViewController.m
#import "HomeTableViewController.h"
#import "AFNetworking.h"
#import "XHNews.h"
#import "XHCell.h"
#import "UIImageView+WebCache.h"
#import "SVPullToRefresh.h"

@interface HomeTableViewController ()
- (IBAction)refresh:(id)sender;
@property (nonatomic, retain) NSMutableArray *dataArray;
@property (nonatomic, assign) NSInteger page;
@end

@implementation HomeTableViewController
- (void)dealloc
{
    [_dataArray release];
    [super dealloc];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    self.page = 1;
    self.dataArray = [NSMutableArray arrayWithCapacity:20];
    
    //下拉刷新
    [self.tableView addPullToRefreshWithActionHandler:^{
        NSLog(@"下拉");
        self.page = 1;
        [self refresh:nil];
    }];
    
    //自动刷新
    [self.tableView triggerPullToRefresh];
    
    //上拉加载更多
    [self.tableView addInfiniteScrollingWithActionHandler:^{
        NSLog(@"加载更多");
        self.page++;
        [self refresh:nil];
    }];

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.dataArray.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    XHCell *cell = [tableView dequeueReusableCellWithIdentifier:@"XHNews" forIndexPath:indexPath];
    cell.bgView.layer.cornerRadius = 7;
    XHNews *news = _dataArray[indexPath.row];
    cell.titleLabel.text = news.title;
    cell.contentLabel.text = news.desc;
    SDWebImage, 图片异步加载的类库, 支持图片下载, 自动缓存, 并且对UIImageView类写了分类(Category), 使用方便
//同步加载图片
//    cell.photoView.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:news.hot_pic]]];
 异步加载图片
[cell.photoView sd_setImageWithURL:[NSURL URLWithString:news.hot_pic] placeholderImage:[UIImage imageNamed:@"none.jpg"]];
    return cell;
}

- (IBAction)refresh:(id)sender {
    //网络请求(异步get)
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.bjnews.com.cn/api/get_hotlist.php?page=1"]];
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue]     completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        NSLog(@"%@", data);
        //JSON解析
        NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:nil];
        NSLog(@"%@", dic);
    }];

   网络类AFNetWorking, 基于Foundation框架
    1.iOS8之前是基于NSURLConnection和NSOperation
    2.iOS9开始是基于NSURLSession和NSOperation
    ARC和MRC之间的修改
   如果你的项目使用的非ARC模式，则为ARC模式的代码文件加入-fobjc-arc标签。
   如果你的项目使用的ARC模式，则为非ARC模式的代码文件加入 -fno-objc-arc标签。
   添加标签的方法:
    1.打开：你的target - Bulid Phases -Compile Sources。
    2.双击对应的*.m文件。
    3.在弹出的窗口中输入上面提到的标签 -fobjc-arc / -fno-objc-arc.
    4.直接按Enter键保存
   
    //发起网络请求
    AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
    当content-type不识别时, 可以设置contenttype类型
    manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/html"];
    //异步get请求, 自动解析JSON数据
    NSString *string = [NSString stringWithFormat:@"http://www.bjnews.com.cn/api/get_hotlist.php?page=%ld", _page];
    [manager GET:string parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
        //成功时执行
        //判断是不是下拉刷新, 如果是, 清空内容
        if (self.page == 1) {
            [self.dataArray removeAllObjects];
        } 
        //数据封装
        NSDictionary *dic = responseObject;
        for (NSDictionary *dictionary in dic[@"list"]) {
            //1
//            XHNews *news = [[XHNews alloc] init];
//            [news setValuesForKeysWithDictionary:dictionary];
           
            //2.
            XHNews *news = [[XHNews alloc] initWithDictionary:dictionary];
            [self.dataArray addObject:news];
            [news release];
            [self.tableView reloadData];
            //停止loading
            [self.tableView.pullToRefreshView stopAnimating];
            [self.tableView.infiniteScrollingView stopAnimating];
        }
        NSLog(@"%@", _dataArray);
        
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        //失败时执行
        NSLog(@"Error: %@", error);
    }];
}
@end