NSOperation下载图片-03

自定义Operation

.h

#import <Foundation/Foundation.h>
@class HMDownloadOperation;

@protocol HMDownloadOperationDelegate <NSObject>

@optional
- (void)downloadOperation:(HMDownloadOperation *)operation didFinishDownload:(UIImage *)image;

@end

@interface HMDownloadOperation : NSOperation
/**
 *  图片的url
 */
@property (nonatomic, copy) NSString *imageUrl;

/**
 *  图片所在的行
 */
@property (nonatomic, strong) NSIndexPath *indexPath;

/**
 *  HMDownloadOperation的代理
 */
@property (nonatomic, weak) id<HMDownloadOperationDelegate> delegate;
@end

.m

#import <UIKit/UIKit.h>
#import "HMDownloadOperation.h"

@implementation HMDownloadOperation
- (void)main
{
    @autoreleasepool {
        if(self.isCancelled) return;
        
        NSURL *url = [NSURL URLWithString:self.imageUrl];
        NSData *data = [NSData dataWithContentsOfURL:url]; // 下载图片
        UIImage *image = [UIImage imageWithData:data];     // data->image
        
        if(self.isCancelled) return;
        
        // 回到主线程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            if([self.delegate respondsToSelector:@selector(downloadOperation:didFinishDownload:)])
            {
                [self.delegate downloadOperation:self didFinishDownload:image];
            }
        }];
    }
}
@end