多图片下载

//
//  ViewController.m
//  多图下载案例
//
//  Created by kun on 16/8/11.
//  Copyright © 2016年 kun. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()
@property (nonatomic, strong) NSArray *apps;
@property (nonatomic, strong) NSMutableDictionary *images;
@property (nonatomic, strong) NSOperationQueue *queue;
@property (nonatomic, strong) NSMutableDictionary *operations;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return self.apps.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *identify = @"apps";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:identify];
    if ( !cell )
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:identify];
    }
    NSDictionary *dict = self.apps[indexPath.row];
    cell.textLabel.text = dict[@"name"];
    cell.detailTextLabel.text = dict[@"download"];
    __block UIImage *image = [self.images objectForKey:dict[@"icon"]];
    if ( !image )
    {
        NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
        NSString *fileName = [dict[@"icon"] lastPathComponent];
        NSString *fullPath = [caches stringByAppendingPathComponent:fileName];
        __block NSData *imageData = [NSData dataWithContentsOfFile:fullPath];
        if ( !imageData )
        {
            NSBlockOperation *cacheOperation = [self.operations objectForKey:dict[@"icon"]];
            if ( !cacheOperation )
            {
                NSBlockOperation *download = [NSBlockOperation blockOperationWithBlock:^{
                    NSURL *url = [NSURL URLWithString:dict[@"icon"]];
                    imageData = [NSData dataWithContentsOfURL:url];
                    [imageData writeToFile:fullPath atomically:YES];
                    image = [UIImage imageWithData:imageData];
                    if ( !image )
                    {
                        [self.operations removeObjectForKey:dict[@"icon"]];
                        return;
                    }
                    [self.images setObject:image forKey:dict[@"icon"]];
                    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
                        [tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
                    }];
                    [self.operations removeObjectForKey:dict[@"icon"]];
                }];
                [self.operations setObject:download forKey:dict[@"icon"]];
                [self.queue addOperation:download];
            }
        }
        else
        {
            image = [UIImage imageWithData:imageData];
            [self.images setObject:image forKey:dict[@"icon"]];
        }
        
    }
    cell.imageView.image = image;
    return cell;
}

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

- (NSArray *)apps
{
    if ( !_apps )
    {
        NSArray *temp = [NSArray arrayWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"apps.plist" ofType:nil]];
        NSMutableArray *arrayM = [NSMutableArray arrayWithArray:temp];
        _apps = arrayM;
    }
    return _apps;
}
- (NSMutableDictionary *)images
{
    if ( !_images )
    {
        _images = [NSMutableDictionary dictionary];
    }
    return _images;
}
- (NSOperationQueue *)queue
{
    if ( !_queue )
    {
        _queue = [[NSOperationQueue alloc] init];
        [_queue setMaxConcurrentOperationCount:5];
    }
    return _queue;
}
- (NSMutableDictionary *)operations
{
    if ( !_operations )
    {
        _operations = [NSMutableDictionary dictionary];
    }
    return _operations;
}
/**
 Documents:会备份，不允许
 Library：
    Caches：缓存文件
    Preferences：偏好设置，保存帐号
 tem：临时文件夹，随时会被删除
 */
@end