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实现iOS图片等资源文件的热更新化(四): 一个最小化的补丁更新逻辑
简介
以前写过一个补丁更新的文章,此处会做一个更精简的最小化实现,以便于集成.为了使逻辑具有通用性,将剥离对AFNetworking和ReativeCocoa的依赖.原来的文章,可以先看这里: http://www.ios122.com/2015/12/jspatconline/
这么做的意义
先交代动机和意义,或许应该成为自己博客的一个标准框架内容之一,不然以后自己需要看着,也不过是一堆干瘪的代码.基本的逻辑图,如上!此处,我就从简!
从简的原因有3:
- 补丁更新,状态可以设计的很复杂,就像开头那篇文章提到的那样,但是我感觉没多大必要,至少在我们的App中;
- 我想演示一个相对完整的逻辑,但是又不想耗费太多的时间构建场景;
- 从简后的方案,简单但够用了,至少目前针对我们的项目来说;
所以说:这篇文章的意义,其实是在于简化已有的热更新代码,越简单越好维护.
基本思路
- App启动时,判断特定的服务器接口所返回的图片url是否为最新,判断方式就是比对返回值中的md5字段与本地保存的资源的url是否一致;
- 如果图片资源有更新,则下载解压到指定的缓存目录,初步打算以资源文件的md5来划分文件夹,来避免冲突;
- 读取图片时,优先从缓存目录读取,缓存目录不存在再从ipa资源包中读取;
下面就一步一步来实现了.
App启动时,判断有无最新图片资源
此处主要涉及到的可能的技术点:
1. 如何用基础的网络类库发送网络请求?
先简单封装一个函数来获取,用到了block.block经常用,但到现在都记不太清形式,大都是从其他处copy下,然后改改参数.记不住,也懒得记!
- (void)fetchPatchInfo:(NSString *) urlStr completionHandler:(void (^)(NSDictionary * patchInfo, NSError * error))completionHandler{ NSURLSessionConfiguration * defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession * defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]]; NSURL * url = [NSURL URLWithString:urlStr]; NSURLSessionDataTask * dataTask = [defaultSession dataTaskWithURL:url completionHandler:^(NSData * data, NSURLResponse * response, NSError * error) { NSDictionary * patchInfo = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];; completionHandler(patchInfo, error); }]; [dataTask resume];}
基于block,调用的代码也就很简答了.
[self fetchPatchInfo: @"https://raw.githubusercontent.com/ios122/ios_assets_hot_update/master/res/patch_04.json" completionHandler:^(NSDictionary * patchInfo, NSError * error) { if ( ! error) { NSLog(@"patchInfo:%@", patchInfo); }else { NSLog(@"fetchPatchInfo error: %@", error); } }];
好吧,我承认AFNetworking用习惯了,好久没用原始的网络请求的代码了,有点low,莫怪!
2. 如何校验下载的文件的md5值,如果你需要的话?
开头那篇文章链接里,有提到.核心,其实是在于下载文件之后,md5值的计算,剩余的就是字符串比较操作了.
注意要先引入系统库
#include <CommonCrypto/CommonDigest.h>
/** * 获取文件的md5信息. * * @param path 文件路径. * * @return 文件的md5值. */-(NSString *)mcMd5HashOfPath:(NSString *)path{ NSFileManager * fileManager = [NSFileManager defaultManager]; // 确保文件存在. if( [fileManager fileExistsAtPath:path isDirectory:nil] ) { NSData * data = http://www.mamicode.com/[NSData dataWithContentsOfFile:path];"%02x", digest[i]]; } return output; } else { return @""; }}
3. 使用什么保存与获取本地缓存资源的md5等信息?
好吧,我打算直接使用用户配置文件,
NSString * source_patch_key = @"SOURCE_PATCH";[[NSUserDefaults standardUserDefaults] setObject:patchInfo forKey: source_patch_key];patchInfo = [[NSUserDefaults standardUserDefaults] objectForKey: source_patch_key];NSLog(@"patchInfo:%@", patchInfo);
补丁下载与解压
此处主要涉及到的可能的技术点:
1. 如何基于图片缓存信息来找到指定的缓存目录?
问题本身有些绕口,其实我想做的就是根据补丁的md5,放到不同的缓存文件夹,如补丁md5为 e963ed645c50a004697530fa596f180b,则对应放到 patch/e963ed645c50a004697530fa596f180b 文件夹.封装一个简单的根据md5返回缓存路径的方法吧:
- (NSString *)cachePathFor:(NSString * )patchMd5{ NSArray * LibraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); NSString * cachePath = [[[LibraryPaths objectAtIndex:0] stringByAppendingFormat:@"/Caches/patch"] stringByAppendingPathComponent:patchMd5]; return cachePath;}
使用时,类似这样:
NSString * urlStr = [patchInfo objectForKey: @"url"];[weak_self downloadFileFrom:urlStr completionHandler:^(NSURL * location, NSError * error) { if (error) { NSLog(@"download file url:%@ error: %@", urlStr, error); return; } NSString * cachePath = [weak_self cachePathFor: [patchInfo objectForKey:@"md5"]]; NSLog(@"location:%@ cachePath:%@",location, cachePath);}];
2. 如何解压文件到指定目录?
如果需要安装 CocoaPods ,建议使用 brew
:
brew install CocoaPods
解压本身推荐 SSZipArchive 库,一行代码搞定:
[SSZipArchive unzipFileAtPath:location.path toDestination: patchCachePath overwrite:YES password:nil error:&error];
3. 在什么时候更新本地的缓存资源的相关信息?
建议是在下载并解压资源文件到指定缓存目录后,再更新补丁的相关缓存信息,因为这个信息,读取图片时,也是需要的.如果删除某个补丁,按照目前的设计,一种比较偷懒的方案就是,在服务器上放上一个新的空资源文件就可以了.
NSString * source_patch_key = @"SOURCE_PATCH";[[NSUserDefaults standardUserDefaults] setObject:patchInfo forKey: source_patch_key];
读取图片功能扩展
此处主要涉及到的可能的技术点:
1. 如何用基础的网络类库下载文件?
依然是要封装一个简单函数,下载完成后,通过block传出文件临时的保存位置:
-(void) downloadFileFrom:(NSString * ) urlStr completionHandler: (void (^)(NSURL *location, NSError * error)) completionHandler{ NSURL * url = [NSURL URLWithString:urlStr]; NSURLSessionConfiguration * defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession * defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate:self delegateQueue: [NSOperationQueue mainQueue]]; NSURLSessionDownloadTask * downloadTask =[ defaultSession downloadTaskWithURL:url completionHandler:^(NSURL * location, NSURLResponse * response, NSError * error) { completionHandler(location,error); }]; [downloadTask resume];}
2. 如何判断bundle中是否含有某文件?
可以使用 fileExistsAtPath,但其实使用 -pathForResource: ofType: 就够了,因为找不到资源问加你时,它返回nil,所以我们直接调用它,然后判断返回是否为 nil 即可:
NSString * imgPath = [mainBundle pathForResource:imgName ofType:@"png"];
3. 将代码如何与原有的imageNamed:逻辑合并?
不需要初始复制到缓存目录 + 初始请求最新的资源补丁信息 + 代码迁移合并 + 接口优化
相对完整的逻辑代码
注意,按照目前的设计,就不需要初始把原来ipa中的bundle复制到缓存目录了;当缓存目录中没有相关资源时,会自动尝试从ipa中的bundle读取,bundle约定统一使用 main.bundle 来简化操作,
类目,对外暴露两个方法:
#import <UIKit/UIKit.h>@interface UIImage (imageNamed_bundle_)/* load img smart .*/+ (UIImage *)yf_imageNamed:(NSString *)imgName;/* smart update for patch */+ (void)yf_updatePatchFrom:(NSString *) pathInfoUrlStr;@end
App启动时,或在其他合适的地方,要注意检查有无更新:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { // Override point for customization after application launch. /* fetch pathc info every time */ NSString * patchUrlStr = @"https://raw.githubusercontent.com/ios122/ios_assets_hot_update/master/res/patch_04.json"; [UIImage yf_updatePatchFrom: patchUrlStr]; return YES;}
内部实现,优化了许多,但也算不上复杂:
#import "UIImage+imageNamed_bundle_.h"#import <SSZipArchive.h>@implementation UIImage (imageNamed_bundle_)+ (NSString *)yf_sourcePatchKey{ return @"SOURCE_PATCH";}+ (void)yf_updatePatchFrom:(NSString *) pathInfoUrlStr{ [self yf_fetchPatchInfo: pathInfoUrlStr completionHandler:^(NSDictionary *patchInfo, NSError *error) { if (error) { NSLog(@"fetchPatchInfo error: %@", error); return; } NSString * urlStr = [patchInfo objectForKey: @"url"]; NSString * md5 = [patchInfo objectForKey:@"md5"]; NSString * oriMd5 = [[[NSUserDefaults standardUserDefaults] objectForKey: [self yf_sourcePatchKey]] objectForKey:@"md5"]; if ([oriMd5 isEqualToString:md5]) { // no update return; } [self yf_downloadFileFrom:urlStr completionHandler:^(NSURL *location, NSError *error) { if (error) { NSLog(@"download file url:%@ error: %@", urlStr, error); return; } NSString * patchCachePath = [self yf_cachePathFor: md5]; [SSZipArchive unzipFileAtPath:location.path toDestination: patchCachePath overwrite:YES password:nil error:&error]; if (error) { NSLog(@"unzip and move file error, with urlStr:%@ error:%@", urlStr, error); return; } /* update patch info. */ NSString * source_patch_key = [self yf_sourcePatchKey]; [[NSUserDefaults standardUserDefaults] setObject:patchInfo forKey: source_patch_key]; }]; }];}+ (NSString *)yf_relativeCachePathFor:(NSString *)md5{ return [@"patch" stringByAppendingPathComponent:md5];}+ (UIImage *)yf_imageNamed:(NSString *)imgName{ NSString * bundleName = @"main"; /* cache dir */ NSString * md5 = [[[NSUserDefaults standardUserDefaults] objectForKey: [self yf_sourcePatchKey]] objectForKey:@"md5"]; NSString * relativeCachePath = [self yf_relativeCachePathFor: md5]; return [self yf_imageNamed: imgName bundle:bundleName cacheDir: relativeCachePath];}+ (UIImage *)yf_imageNamed:(NSString *)imgName bundle:(NSString *)bundleName cacheDir:(NSString *)cacheDir{ NSArray * LibraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); bundleName = [NSString stringWithFormat:@"%@.bundle",bundleName]; NSString * ipaBundleDir = [NSBundle mainBundle].resourcePath; NSString * cacheBundleDir = ipaBundleDir; if (cacheDir) { cacheBundleDir = [[[LibraryPaths objectAtIndex:0] stringByAppendingFormat:@"/Caches"] stringByAppendingPathComponent:cacheDir]; } imgName = [NSString stringWithFormat:@"%@@3x",imgName]; NSString * bundlePath = [cacheBundleDir stringByAppendingPathComponent: bundleName]; NSBundle * mainBundle = [NSBundle bundleWithPath:bundlePath]; NSString * imgPath = [mainBundle pathForResource:imgName ofType:@"png"]; /* try load from ipa! */ if ( ! imgPath && ! [ipaBundleDir isEqualToString: cacheBundleDir]) { bundlePath = [ipaBundleDir stringByAppendingPathComponent: bundleName]; mainBundle = [NSBundle bundleWithPath:bundlePath]; imgPath = [mainBundle pathForResource:imgName ofType:@"png"]; } UIImage * image; static NSString * model; if (!model) { model = [[UIDevice currentDevice]model]; } if ([model isEqualToString:@"iPad"]) { NSData * imageData = [NSData dataWithContentsOfFile: imgPath]; image = [UIImage imageWithData:imageData scale:2.0]; }else{ image = [UIImage imageWithContentsOfFile: imgPath]; } return image;}+ (void)yf_fetchPatchInfo:(NSString *) urlStr completionHandler:(void (^)(NSDictionary * patchInfo, NSError * error))completionHandler{ NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: nil delegateQueue: [NSOperationQueue mainQueue]]; NSURL * url = [NSURL URLWithString:urlStr]; NSURLSessionDataTask * dataTask = [defaultSession dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { NSDictionary * patchInfo = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];; completionHandler(patchInfo, error); }]; [dataTask resume];}+ (void) yf_downloadFileFrom:(NSString * ) urlStr completionHandler: (void (^)(NSURL *location, NSError * error)) completionHandler{ NSURL * url = [NSURL URLWithString:urlStr]; NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate:nil delegateQueue: [NSOperationQueue mainQueue]]; NSURLSessionDownloadTask * downloadTask =[ defaultSession downloadTaskWithURL:url completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) { completionHandler(location,error); }]; [downloadTask resume];}+ (NSString *)yf_cachePathFor:(NSString * )patchMd5{ NSArray * LibraryPaths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES); NSString * cachePath = [[[LibraryPaths objectAtIndex:0] stringByAppendingFormat:@"/Caches"] stringByAppendingPathComponent:[self yf_relativeCachePathFor: patchMd5]]; return cachePath;}@end
现在,加载图片的代码更简单了:
UIImage * image = [UIImage yf_imageNamed:@"sub/sample"];self.sampleImageView.image = image;
如果热更新生效,运行看到的应该是一个锤子图片:
后记
我觉得,这篇文章最大的特点是,完整记录了一次优化解决问题的过程;示例代码看起来前后有些不太统一,是因为: 我不是先有了方案再写博客,而是借助博客本身来梳理思路,简化逻辑!如此,写博客,就不单单是一个耗时的分享知识的过程,更成为了一个帮助自己思考的有力工具!赞!!!
参考资源:
- 本节内容完整可执行Xcode工程代码,不到100k
- 系列文章,专属github项目
- iOS NSURLSession Example (HTTP GET, POST, Background Downlads )
- 价值100W的经验分享: 基于JSPatch的iOS应用线上Bug的即时修复方案,附源码.
- ZipArchive is a simple utility class for zipping and unzipping files on iOS and Mac.
- pod 的安装和使用
实现iOS图片等资源文件的热更新化(四): 一个最小化的补丁更新逻辑