仿照SDWebImage 内部核心实现

//
//  CKWebImage.h
//  UI高级2
//
//  Created by Jason_Msbaby on 15/10/12.
//  Copyright © 2015年 张杰. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface CKWebImage : NSObject

+(instancetype)defaultLoader;

-(void)downLoader:(NSString *)path FinishHandle:(void(^)(UIImage *img))block;

@end

/**
*  UIImageView拓展类目
*/
@interface UIImageView (CKWebImage)

-(void)ck_setImageWithURL:(NSString *)url;

-(void)ck_setImageWithURL:(NSString *)url placeholderImage:(UIImage *)hoderImage;

@end

//
//  CKWebImage.m
//  UI高级2
//
//  Created by Jason_Msbaby on 15/10/12.
//  Copyright © 2015年 张杰. All rights reserved.
//

#import "CKWebImage.h"
#import <CommonCrypto/CommonCrypto.h>

@interface CKWebImage ()
@property(nonatomic, strong) NSMutableArray *history;// The DownLoad file History
@end

@implementation CKWebImage

static CKWebImage *handle;

+(instancetype)defaultLoader{

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
handle = [CKWebImage new];
});
return handle;
}

- (instancetype)init
{
self = [super init];
if (self) {
self.history = [NSMutableArray array];
}
return self;
}

-(void)downLoader:(NSString *)path FinishHandle:(void (^)(UIImage *))block{
if (!block || !path) {
NSLog(@"参数有误");
return ;
}
NSString *imageMD5Name = [self parseMD5:path];
//get the cache path in the phone
NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).firstObject;
NSString *fileName = [cachePath stringByAppendingPathComponent:imageMD5Name];

if ([self.history containsObject:imageMD5Name]) {
NSData *data = [NSData dataWithContentsOfFile:fileName];
UIImage *img = [UIImage imageWithData:data];
block(img);
NSLog(@"本地");
}else{
NSURL *url = [NSURL URLWithString:path];
NSURLSessionDataTask *dataTask = [[NSURLSession sharedSession]dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
if (error || !data) {
NSLog(@"请求出错");
return ;
}
//download success
[data writeToFile:fileName atomically:YES];
[self.history addObject:imageMD5Name];
NSLog(@"网络");
UIImage *img = [UIImage imageWithData:data];
//            sleep(3);
dispatch_sync(dispatch_get_main_queue(), ^{
block(img);
});
}];
[dataTask resume];
}
}

//parse str to md5 and return md5encoding
-(NSString*)parseMD5:(NSString *)str{
unsigned char result[16];
const char *sourceData = str.UTF8String;
CC_MD5(sourceData,strlen(sourceData), result);
NSMutableString *res = [NSMutableString string];
for (int i = 0; i < 16; i++) {
[res appendString:[NSString stringWithFormat:@"%x",result[i]]];
}
return  res;
}

@end

@implementation UIImageView (CKWebImage)

-(void)ck_setImageWithURL:(NSString *)url{
[self ck_setImageWithURL:url placeholderImage:nil];
}

-(void)ck_setImageWithURL:(NSString *)url placeholderImage:(UIImage *)hoderImage{
self.image = hoderImage;
__weak UIImageView *weakImageView = self;
[[CKWebImage defaultLoader]downLoader:url FinishHandle:^(UIImage *img) {
weakImageView.image = img;
}];
}

@end