AFNetworking2.0源码解析AFURLResponseSerialization
来源：互联网 发布：2014年马刺数据 编辑：程序博客网 时间：2024/05/16 18:14
续AFNetworking2.0源码解析<一><二><三>，本篇来看看AFURLResponseSerialization做的事情。
结构
AFURLResponseSerialization负责解析网络返回数据，检查数据是否合法，把NSData数据转成相应的对象，内置的转换器有json,xml,plist,image，用户可以很方便地继承基类AFHTTPResponseSerializer去解析更多的数据格式，AFNetworking这一套响应解析机制结构很简单，主要就是两个方法：
1.-validateResponse:data:error:
基类AFHTTPResponseSerializer的这个方法检测返回的HTTP状态码和数据类型是否合法，属性acceptableStatusCodes和acceptableContentTypes规定了合法的状态码和数据类型，例如JSONSerialization就把acceptableContentTypes设为@”application/json”, @”text/json”, @”text/javascript”，若不是这三者之一，就验证失败，返回相应的NSError对象。一般子类不需要重写这个方法，只需要设置好acceptableStatusCodes和acceptableContentTypes就行了。
2.-responseObjectForResponse:data:error:
这个方法解析数据，把NSData转成相应的对象，上层AFURLConnectionOperation会调用这个方法获取转换后的对象。
在解析数据之前会先调上述的validateResponse方法检测HTTP响应是否合法，要注意的是即使这里检测返回不合法，也会继续解析数据生成对象，因为有可能错误信息就在返回的数据里。
如果validateResponse返回error，这里的解析数据又出错，这时有两个error对象，怎样返回给上层？这里的处理是把解析数据的NSError对象保存到validateResponse NSError的userInfo里，作为UnderlyingError，NSError专门给了个NSUnderlyingErrorKey作为这种错误包含错误的键值。
剩下的就是NSecureCoding相关方法了，如果子类增加了property，需要加上相应的NSecureCoding方法。
JSON解析
AFJSONResponseSerializer使用系统内置的NSJSONSerialization解析json，NSJSON只支持解析UTF8编码的数据（还有UTF-16LE之类的，都不常用），所以要先把返回的数据转成UTF8格式。这里会尝试用HTTP返回的编码类型和自己设置的stringEncoding去把数据解码转成字符串NSString，再把NSString用UTF8编码转成NSData，再用NSJSONSerialization解析成对象返回。
上述过程是NSData->NSString->NSData->NSObject，这里有个问题，如果你能确定服务端返回的是UTF8编码的json数据，那NSData->NSString->NSData这两步就是无意义的，而且这两步进行了两次编解码，很浪费性能，所以如果确定服务端返回utf8编码数据，就建议自己再写个JSONResponseSerializer，跳过这两个步骤。
此外AFJSONResponseSerializer专门写了个方法去除NSNull，直接把对象里值是NSNull的键去掉，还蛮贴心，若不去掉，上层很容易忽略了这个数据类型，判断了数据是否nil没判断是否NSNull，进行了错误的调用导致core。
图片解压
当我们调用UIImage的方法imageWithData:方法把数据转成UIImage对象后，其实这时UIImage对象还没准备好需要渲染到屏幕的数据，现在的网络图像PNG和JPG都是压缩格式，需要把它们解压转成bitmap后才能渲染到屏幕上，如果不做任何处理，当你把UIImage赋给UIImageView，在渲染之前底层会判断到UIImage对象未解压，没有bitmap数据，这时会在主线程对图片进行解压操作，再渲染到屏幕上。这个解压操作是比较耗时的，如果任由它在主线程做，可能会导致速度慢UI卡顿的问题。
AFImageResponseSerializer除了把返回数据解析成UIImage外，还会把图像数据解压，这个处理是在子线程（AFNetworking专用的一条线程，详见AFURLConnectionOperation），处理后上层使用返回的UIImage在主线程渲染时就不需要做解压这步操作，主线程减轻了负担，减少了UI卡顿问题。
具体实现上在AFInflatedImageFromResponseWithDataAtScale里，创建一个画布，把UIImage画在画布上，再把这个画布保存成UIImage返回给上层。只有JPG和PNG才会尝试去做解压操作，期间如果解压失败，或者遇到CMKY颜色格式的jpg，或者图像太大(解压后的bitmap太占内存，一个像素3-4字节，搞不好内存就爆掉了)，就直接返回未解压的图像。
另外在代码里看到iOS才需要这样手动解压，MacOS上已经有封装好的对象NSBitmapImageRep可以做这个事。
关于图片解压，还有几个问题不清楚：
1.本来以为调用imageWithData方法只是持有了数据，没有做解压相关的事，后来看到调用堆栈发现已经做了一些解压操作，从调用名字看进行了huffman解码，不知还会继续做到解码jpg的哪一步。 
2.以上图片手动解压方式都是在CPU进行的，如果不进行手动解压，把图片放进layer里，让底层自动做这个事，是会用GPU进行的解压的。不知用GPU解压与用CPU解压速度会差多少，如果GPU速度很快，就算是在主线程做解压，也变得可以接受了，就不需要手动解压这样的优化了，不过目前没找到方法检测GPU解压的速度。
P.S. 关于图片解压，有篇挺挺不错的文章：Avoiding Image Decompression Sickness
源码注释
// AFSerialization.h//// Copyright (c) 2013-2014 AFNetworking (http://afnetworking.com)//// Permission is hereby granted, free of charge, to any person obtaining a copy// of this software and associated documentation files (the "Software"), to deal// in the Software without restriction, including without limitation the rights// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell// copies of the Software, and to permit persons to whom the Software is// furnished to do so, subject to the following conditions:// // The above copyright notice and this permission notice shall be included in// all copies or substantial portions of the Software.// // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN// THE SOFTWARE.#import "AFURLResponseSerialization.h"#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)#import <UIKit/UIKit.h>#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED)#import <Cocoa/Cocoa.h>#endifNSString * const AFURLResponseSerializationErrorDomain = @"com.alamofire.error.serialization.response";NSString * const AFNetworkingOperationFailingURLResponseErrorKey = @"com.alamofire.serialization.response.error.response";//把一个NSError对象作为另一个NSError的附属Error，放在userInfo的NSUnderlyingErrorKey键里static NSError * AFErrorWithUnderlyingError(NSError *error, NSError *underlyingError) { if (!error) { return underlyingError; } if (!underlyingError || error.userInfo[NSUnderlyingErrorKey]) { return error; } NSMutableDictionary *mutableUserInfo = [error.userInfo mutableCopy]; mutableUserInfo[NSUnderlyingErrorKey] = underlyingError; return [[NSError alloc] initWithDomain:error.domain code:error.code userInfo:mutableUserInfo];}//NSError对象是否指定domain和code，把UnderlyingError也给判断了static BOOL AFErrorOrUnderlyingErrorHasCodeInDomain(NSError *error, NSInteger code, NSString *domain) { if ([error.domain isEqualToString:domain] && error.code == code) { return YES; } else if (error.userInfo[NSUnderlyingErrorKey]) { return AFErrorOrUnderlyingErrorHasCodeInDomain(error.userInfo[NSUnderlyingErrorKey], code, domain); } return NO;}//删除JSON NSDictionary数据里的NSNull对象，直接去掉这个键static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingOptions readingOptions) { if ([JSONObject isKindOfClass:[NSArray class]]) { NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:[(NSArray *)JSONObject count]]; for (id value in (NSArray *)JSONObject) { [mutableArray addObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions)]; } return (readingOptions & NSJSONReadingMutableContainers) ? mutableArray : [NSArray arrayWithArray:mutableArray]; } else if ([JSONObject isKindOfClass:[NSDictionary class]]) { NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:JSONObject]; for (id <NSCopying> key in [(NSDictionary *)JSONObject allKeys]) { id value = [(NSDictionary *)JSONObject objectForKey:key]; if (!value || [value isEqual:[NSNull null]]) { [mutableDictionary removeObjectForKey:key]; } else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]]) { [mutableDictionary setObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions) forKey:key]; } } return (readingOptions & NSJSONReadingMutableContainers) ? mutableDictionary : [NSDictionary dictionaryWithDictionary:mutableDictionary]; } return JSONObject;}@implementation AFHTTPResponseSerializer+ (instancetype)serializer { return [[self alloc] init];}- (instancetype)init { self = [super init]; if (!self) { return nil; } //默认UTF8编码，若HTTP Response里没有encoding数据，会用这个编码去解码数据 self.stringEncoding = NSUTF8StringEncoding; //只接受HTTP状态码2xx，2xx在HTTP状态码里表示请求成功 self.acceptableStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(200, 100)]; //默认任何数据类型都接受 self.acceptableContentTypes = nil; return self;}#pragma mark -- (BOOL)validateResponse:(NSHTTPURLResponse *)response data:(NSData *)data error:(NSError * __autoreleasing *)error{ BOOL responseIsValid = YES; NSError *validationError = nil; if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) { if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]]) { //返回的数据类型不在定义的acceptableContentTypes里，不合法 if ([data length] > 0) { //如果有数据，给出一个 不能解码 的NSError //responseObjectForResponse里若判断到是这个Error，就不解析数据了 NSDictionary *userInfo = @{ NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]], NSURLErrorFailingURLErrorKey:[response URL], AFNetworkingOperationFailingURLResponseErrorKey: response }; validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo], validationError); } //如果连数据都没有，就没数据类型什么事了，不算error responseIsValid = NO; } if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode]) { //返回的HTTP状态码不在可接受范围内 NSDictionary *userInfo = @{ NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode], NSURLErrorFailingURLErrorKey:[response URL], AFNetworkingOperationFailingURLResponseErrorKey: response }; validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:userInfo], validationError); responseIsValid = NO; } } if (error && !responseIsValid) { *error = validationError; } return responseIsValid;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ [self validateResponse:(NSHTTPURLResponse *)response data:data error:error]; return data;}#pragma mark - NSecureCoding//用于对象序列化保存和反序列化取出的NSecureCoding方法们，以及用于copy的copyWithZone方法//子类若有新增属性，需要一个个写上+ (BOOL)supportsSecureCoding { return YES;}- (id)initWithCoder:(NSCoder *)decoder { self = [self init]; if (!self) { return nil; } self.acceptableStatusCodes = [decoder decodeObjectOfClass:[NSIndexSet class] forKey:NSStringFromSelector(@selector(acceptableStatusCodes))]; self.acceptableContentTypes = [decoder decodeObjectOfClass:[NSIndexSet class] forKey:NSStringFromSelector(@selector(acceptableContentTypes))]; return self;}- (void)encodeWithCoder:(NSCoder *)coder { [coder encodeObject:self.acceptableStatusCodes forKey:NSStringFromSelector(@selector(acceptableStatusCodes))]; [coder encodeObject:self.acceptableContentTypes forKey:NSStringFromSelector(@selector(acceptableContentTypes))];}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFHTTPResponseSerializer *serializer = [[[self class] allocWithZone:zone] init]; serializer.acceptableStatusCodes = [self.acceptableStatusCodes copyWithZone:zone]; serializer.acceptableContentTypes = [self.acceptableContentTypes copyWithZone:zone]; return serializer;}@end#pragma mark -@implementation AFJSONResponseSerializer+ (instancetype)serializer { return [self serializerWithReadingOptions:0];}+ (instancetype)serializerWithReadingOptions:(NSJSONReadingOptions)readingOptions { AFJSONResponseSerializer *serializer = [[self alloc] init]; serializer.readingOptions = readingOptions; return serializer;}- (instancetype)init { self = [super init]; if (!self) { return nil; } self.acceptableContentTypes = [NSSet setWithObjects:@"application/json", @"text/json", @"text/javascript", nil]; return self;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ //先调基类的方法验证response是否有错误， if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) { //若验证不通过，但又没有错误信息，不知道是什么错误，直接返回 //若是数据类型错误，不进行数据的解析，直接返回，否则要解析数据，因为数据里可能有错误信息。 if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) { return nil; } } // Workaround for behavior of Rails to return a single space for `head k` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization. // See https://github.com/rails/rails/issues/1742 NSStringEncoding stringEncoding = self.stringEncoding; if (response.textEncodingName) { //优先尝试用HTTP返回的编码类型，没有或不合法才用属性self.stringEncoding的编码类型 CFStringEncoding encoding = CFStringConvertIANACharSetNameToEncoding((CFStringRef)response.textEncodingName); if (encoding != kCFStringEncodingInvalidId) { stringEncoding = CFStringConvertEncodingToNSStringEncoding(encoding); } } id responseObject = nil; NSError *serializationError = nil; @autoreleasepool { //json数据可能比较大，这里responseString分别持有了拷贝，要让它尽快释放，所以加了@autoreleasepool，不用等到整个循环执行完到下个runloop才释放这个大对象 //**先用指定编码类型解码 NSString *responseString = [[NSString alloc] initWithData:data encoding:stringEncoding]; if (responseString && ![responseString isEqualToString:@" "]) { // Workaround for a bug in NSJSONSerialization when Unicode character escape codes are used instead of the actual character // See http://stackoverflow.com/a/12843465/157142 //**再用UTF8编码 data = [responseString dataUsingEncoding:NSUTF8StringEncoding]; if (data) { //data不为nil就是解析成功，若解析成功后字符串长度为0，就不算解析失败，直接返回object为nil if ([data length] > 0) { //**最后转成NSArray/NSDictiony对象 responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError]; } else { return nil; } } else { //解析失败，构建NSError返回 NSDictionary *userInfo = @{ NSLocalizedDescriptionKey: NSLocalizedStringFromTable(@"Data failed decoding as a UTF-8 string", nil, @"AFNetworking"), NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Could not decode string: %@", nil, @"AFNetworking"), responseString] }; serializationError = [NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:userInfo]; } } } if (self.removesKeysWithNullValues && responseObject) { //清除所有NSNull对象 responseObject = AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions); } if (error) { //如果validateResponse已返回error，把序列化的error对象加到valid的error对象里，作为underlyingError *error = AFErrorWithUnderlyingError(serializationError, *error);; } return responseObject;}#pragma mark - NSecureCoding- (id)initWithCoder:(NSCoder *)decoder { self = [super initWithCoder:decoder]; if (!self) { return nil; } self.readingOptions = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(readingOptions))] unsignedIntegerValue]; return self;}- (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder]; [coder encodeObject:@(self.readingOptions) forKey:NSStringFromSelector(@selector(readingOptions))];}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFJSONResponseSerializer *serializer = [[[self class] allocWithZone:zone] init]; serializer.readingOptions = self.readingOptions; return serializer;}@end#pragma mark -@implementation AFXMLParserResponseSerializer+ (instancetype)serializer { AFXMLParserResponseSerializer *serializer = [[self alloc] init]; return serializer;}- (instancetype)init { self = [super init]; if (!self) { return nil; } self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/xml", @"text/xml", nil]; return self;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSHTTPURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) { if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) { return nil; } } return [[NSXMLParser alloc] initWithData:data];}@end#pragma mark -#ifdef __MAC_OS_X_VERSION_MIN_REQUIRED@implementation AFXMLDocumentResponseSerializer+ (instancetype)serializer { return [self serializerWithXMLDocumentOptions:0];}+ (instancetype)serializerWithXMLDocumentOptions:(NSUInteger)mask { AFXMLDocumentResponseSerializer *serializer = [[self alloc] init]; serializer.options = mask; return serializer;}- (instancetype)init { self = [super init]; if (!self) { return nil; } self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/xml", @"text/xml", nil]; return self;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) { if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) { return nil; } } NSError *serializationError = nil; NSXMLDocument *document = [[NSXMLDocument alloc] initWithData:data options:self.options error:&serializationError]; if (error) { *error = AFErrorWithUnderlyingError(serializationError, *error); } return document;}#pragma mark - NSecureCoding- (id)initWithCoder:(NSCoder *)decoder { self = [super initWithCoder:decoder]; if (!self) { return nil; } self.options = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(options))] unsignedIntegerValue]; return self;}- (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder]; [coder encodeObject:@(self.options) forKey:NSStringFromSelector(@selector(options))];}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFXMLDocumentResponseSerializer *serializer = [[[self class] allocWithZone:zone] init]; serializer.options = self.options; return serializer;}@end#endif#pragma mark -@implementation AFPropertyListResponseSerializer+ (instancetype)serializer { return [self serializerWithFormat:NSPropertyListXMLFormat_v1_0 readOptions:0];}+ (instancetype)serializerWithFormat:(NSPropertyListFormat)format readOptions:(NSPropertyListReadOptions)readOptions{ AFPropertyListResponseSerializer *serializer = [[self alloc] init]; serializer.format = format; serializer.readOptions = readOptions; return serializer;}- (instancetype)init { self = [super init]; if (!self) { return nil; } self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"application/x-plist", nil]; return self;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) { if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) { return nil; } } id responseObject; NSError *serializationError = nil; if (data) { responseObject = [NSPropertyListSerialization propertyListWithData:data options:self.readOptions format:NULL error:&serializationError]; } if (error) { *error = AFErrorWithUnderlyingError(serializationError, *error); } return responseObject;}#pragma mark - NSecureCoding- (id)initWithCoder:(NSCoder *)decoder { self = [super initWithCoder:decoder]; if (!self) { return nil; } self.format = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(format))] unsignedIntegerValue]; self.readOptions = [[decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(readOptions))] unsignedIntegerValue]; return self;}- (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder]; [coder encodeObject:@(self.format) forKey:NSStringFromSelector(@selector(format))]; [coder encodeObject:@(self.readOptions) forKey:NSStringFromSelector(@selector(readOptions))];}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFPropertyListResponseSerializer *serializer = [[[self class] allocWithZone:zone] init]; serializer.format = self.format; serializer.readOptions = self.readOptions; return serializer;}@end#pragma mark -#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED)#import <CoreGraphics/CoreGraphics.h>static UIImage * AFImageWithDataAtScale(NSData *data, CGFloat scale) { //不清楚这里为什么不用[[UIImage alloc] initWithData:data scale:scale]而要创建两次UIImage UIImage *image = [[UIImage alloc] initWithData:data]; return [[UIImage alloc] initWithCGImage:[image CGImage] scale:scale orientation:image.imageOrientation];}static UIImage * AFInflatedImageFromResponseWithDataAtScale(NSHTTPURLResponse *response, NSData *data, CGFloat scale) { if (!data || [data length] == 0) { return nil; } CGImageRef imageRef = NULL; CGDataProviderRef dataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data); if ([response.MIMEType isEqualToString:@"image/png"]) { imageRef = CGImageCreateWithPNGDataProvider(dataProvider, NULL, true, kCGRenderingIntentDefault); } else if ([response.MIMEType isEqualToString:@"image/jpeg"]) { imageRef = CGImageCreateWithJPEGDataProvider(dataProvider, NULL, true, kCGRenderingIntentDefault); // CGImageCreateWithJPEGDataProvider does not properly handle CMKY, so if so, fall back to AFImageWithDataAtScale //英文解释得挺清楚了，如果jpg的色彩空间是CMKY而不是RGB的话，不进行解压 if (imageRef) { CGColorSpaceRef imageColorSpace = CGImageGetColorSpace(imageRef); CGColorSpaceModel imageColorSpaceModel = CGColorSpaceGetModel(imageColorSpace); if (imageColorSpaceModel == kCGColorSpaceModelCMYK) { CGImageRelease(imageRef); imageRef = NULL; } } } CGDataProviderRelease(dataProvider); //这里创建了UIImage对象，用于不符合解压条件时直接返回未解压的UIImage //这里这样创建代码写起来是方便了，但无论符不符合解压条件，这个备用的UIImage都生成了，浪费了性能 UIImage *image = AFImageWithDataAtScale(data, scale); if (!imageRef) { //images是用于做动画的多张图片，如果是这个类型，或者image对象生成失败，直接返回 if (image.images || !image) { return image; } //TODO 为毛要copy呢 imageRef = CGImageCreateCopy([image CGImage]); if (!imageRef) { return nil; } } //获取图片宽高和存储一个像素需要用到的字节数 size_t width = CGImageGetWidth(imageRef); size_t height = CGImageGetHeight(imageRef); size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef); //图片太大了就不解压了，因为解压后bitmap数据一直保存在UIImage对象里，有可能把内存撑爆了 //如果一个像素的字节数大于8也不解压，一般RGBA每个颜色2byte，一共8byte，不清楚什么情况下会有大于8字节的 if (width * height > 1024 * 1024 || bitsPerComponent > 8) { CGImageRelease(imageRef); return image; } //画布的参数 size_t bytesPerRow = 0; // CGImageGetBytesPerRow() calculates incorrectly in iOS 5.0, so defer to CGBitmapContextCreate CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGColorSpaceModel colorSpaceModel = CGColorSpaceGetModel(colorSpace); CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef); if (colorSpaceModel == kCGColorSpaceModelRGB) { uint32_t alpha = (bitmapInfo & kCGBitmapAlphaInfoMask); if (alpha == kCGImageAlphaNone) { bitmapInfo &= ~kCGBitmapAlphaInfoMask; bitmapInfo |= kCGImageAlphaNoneSkipFirst; } else if (!(alpha == kCGImageAlphaNoneSkipFirst || alpha == kCGImageAlphaNoneSkipLast)) { bitmapInfo &= ~kCGBitmapAlphaInfoMask; bitmapInfo |= kCGImageAlphaPremultipliedFirst; } } //生成像素画布 CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo); CGColorSpaceRelease(colorSpace); if (!context) { CGImageRelease(imageRef); return image; } //在画布上画出图片，保存成CGImageRef对象，转成UIImage，完成解压 CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), imageRef); CGImageRef inflatedImageRef = CGBitmapContextCreateImage(context); CGContextRelease(context); UIImage *inflatedImage = [[UIImage alloc] initWithCGImage:inflatedImageRef scale:scale orientation:image.imageOrientation]; CGImageRelease(inflatedImageRef); CGImageRelease(imageRef); return inflatedImage;}#endif@implementation AFImageResponseSerializer- (instancetype)init { self = [super init]; if (!self) { return nil; } self.acceptableContentTypes = [[NSSet alloc] initWithObjects:@"image/tiff", @"image/jpeg", @"image/gif", @"image/png", @"image/ico", @"image/x-icon", @"image/bmp", @"image/x-bmp", @"image/x-xbitmap", @"image/x-win-bitmap", nil];#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED) self.imageScale = [[UIScreen mainScreen] scale]; self.automaticallyInflatesResponseImage = YES;#endif return self;}#pragma mark - AFURLResponseSerializer- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) { if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) { return nil; } }#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED) //iOS需要手动解压 if (self.automaticallyInflatesResponseImage) { return AFInflatedImageFromResponseWithDataAtScale((NSHTTPURLResponse *)response, data, self.imageScale); } else { return AFImageWithDataAtScale(data, self.imageScale); }#elif defined(__MAC_OS_X_VERSION_MIN_REQUIRED) //MacOS直接有内置方法可以解压 // Ensure that the image is set to it's correct pixel width and height NSBitmapImageRep *bitimage = [[NSBitmapImageRep alloc] initWithData:data]; NSImage *image = [[NSImage alloc] initWithSize:NSMakeSize([bitimage pixelsWide], [bitimage pixelsHigh])]; [image addRepresentation:bitimage]; return image;#endif return nil;}#pragma mark - NSecureCoding- (id)initWithCoder:(NSCoder *)decoder { self = [super initWithCoder:decoder]; if (!self) { return nil; }#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED) NSNumber *imageScale = [decoder decodeObjectOfClass:[NSNumber class] forKey:NSStringFromSelector(@selector(imageScale))];#if CGFLOAT_IS_DOUBLE self.imageScale = [imageScale doubleValue];#else self.imageScale = [imageScale floatValue];#endif self.automaticallyInflatesResponseImage = [decoder decodeBoolForKey:NSStringFromSelector(@selector(automaticallyInflatesResponseImage))];#endif return self;}- (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder];#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED) [coder encodeObject:@(self.imageScale) forKey:NSStringFromSelector(@selector(imageScale))]; [coder encodeBool:self.automaticallyInflatesResponseImage forKey:NSStringFromSelector(@selector(automaticallyInflatesResponseImage))];#endif}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFImageResponseSerializer *serializer = [[[self class] allocWithZone:zone] init];#if defined(__IPHONE_OS_VERSION_MIN_REQUIRED) serializer.imageScale = self.imageScale; serializer.automaticallyInflatesResponseImage = self.automaticallyInflatesResponseImage;#endif return serializer;}@end#pragma mark -//可以自动尝试用多个ResponseSerializer解析数据的Serializer@interface AFCompoundResponseSerializer ()@property (readwrite, nonatomic, copy) NSArray *responseSerializers;@end@implementation AFCompoundResponseSerializer+ (instancetype)compoundSerializerWithResponseSerializers:(NSArray *)responseSerializers { AFCompoundResponseSerializer *serializer = [[self alloc] init]; serializer.responseSerializers = responseSerializers; return serializer;}#pragma mark - AFURLResponseSerialization- (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error{ //遍历所有ResponseSerializater，能解析出来就返回，解析不了就尝试下一个 for (id <AFURLResponseSerialization> serializer in self.responseSerializers) { if (![serializer isKindOfClass:[AFHTTPResponseSerializer class]]) { continue; } NSError *serializerError = nil; id responseObject = [serializer responseObjectForResponse:response data:data error:&serializerError]; if (responseObject) { if (error) { *error = AFErrorWithUnderlyingError(serializerError, *error); } return responseObject; } } return [super responseObjectForResponse:response data:data error:error];}#pragma mark - NSecureCoding- (id)initWithCoder:(NSCoder *)decoder { self = [super initWithCoder:decoder]; if (!self) { return nil; } self.responseSerializers = [decoder decodeObjectOfClass:[NSArray class] forKey:NSStringFromSelector(@selector(responseSerializers))]; return self;}- (void)encodeWithCoder:(NSCoder *)coder { [super encodeWithCoder:coder]; [coder encodeObject:self.responseSerializers forKey:NSStringFromSelector(@selector(responseSerializers))];}#pragma mark - NSCopying- (id)copyWithZone:(NSZone *)zone { AFCompoundResponseSerializer *serializer = [[[self class] allocWithZone:zone] init]; serializer.responseSerializers = self.responseSerializers; 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