AFNetworking 3.0源码阅读 - AFURLResponseSerialization

 这次来说一下AFURLResponseSerialization这个HTTP响应类

定义了一个协议，该协议返回序列化后的结果。后续的AFHTTPResponseSerializer以及他的子类都遵循了该协议

该类内有很多子类定义，这里借用一张图来展示，之后一个一个来说

我们先来看下AFHTTPResponseSerializer在头文件中的定义有哪些

可以看到有两个初始化方法，然后stringEncoding后面有一个宏，这个宏代表这弃用了。

 

 来看实现文件的部分

这里有一个NSIndexSet

NSIndexSet：代表一个不可变的独特的无符号整数的集合,称为索引,因为使用它们的方式。这个集合被称为索引集。你不应该使用索引集存储任意集合的整数值,因为索引集按索引排序范围的方式存储的。这使得它们更有效率比存储单个整数的集合。这也意味着每个索引值指数中只能出现一次。通俗点讲NSIndexSet就是一个唯一的，有序的，无符号整数的集合。

self.acceptableStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(200, 100)];

表示接受状态码范围200~299

- (BOOL)validateResponse:(NSHTTPURLResponse *)response
                    data:(NSData *)data
                   error:(NSError * __autoreleasing *)error
{
    BOOL responseIsValid = YES;//默认为yes
    NSError *validationError = nil;

    //存在response且为NSHTTPURLResponse类
    if (response && [response isKindOfClass:[NSHTTPURLResponse class]]) {
        //条件:1.acceptableContentTypes存在 2.response的MIMEType不在范围内 3.MIMEType和data均不为空
        if (self.acceptableContentTypes && ![self.acceptableContentTypes containsObject:[response MIMEType]] &&
            !([response MIMEType] == nil && [data length] == 0)) {

            //data长度大于0且respone的URL存在
            if ([data length] > 0 && [response URL]) {
                //定义错误信息字典
                NSMutableDictionary *mutableUserInfo = [@{
                                                          NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: unacceptable content-type: %@", @"AFNetworking", nil), [response MIMEType]],
                                                          NSURLErrorFailingURLErrorKey:[response URL],
                                                          AFNetworkingOperationFailingURLResponseErrorKey: response,
                                                        } mutableCopy];
                if (data) {
                    //错误信息包含data
                    mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
                }
                //生成NSerror
                validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorCannotDecodeContentData userInfo:mutableUserInfo], validationError);
            }

            responseIsValid = NO;
        }

        if (self.acceptableStatusCodes && ![self.acceptableStatusCodes containsIndex:(NSUInteger)response.statusCode] && [response URL]) {
            NSMutableDictionary *mutableUserInfo = [@{
                                               NSLocalizedDescriptionKey: [NSString stringWithFormat:NSLocalizedStringFromTable(@"Request failed: %@ (%ld)", @"AFNetworking", nil), [NSHTTPURLResponse localizedStringForStatusCode:response.statusCode], (long)response.statusCode],
                                               NSURLErrorFailingURLErrorKey:[response URL],
                                               AFNetworkingOperationFailingURLResponseErrorKey: response,
                                       } mutableCopy];

            if (data) {
                mutableUserInfo[AFNetworkingOperationFailingURLResponseDataErrorKey] = data;
            }

            validationError = AFErrorWithUnderlyingError([NSError errorWithDomain:AFURLResponseSerializationErrorDomain code:NSURLErrorBadServerResponse userInfo:mutableUserInfo], validationError);

            responseIsValid = NO;
        }
    }

    if (error && !responseIsValid) {
        *error = validationError;
    }

    return responseIsValid;
}

response有效性验证过程

NSSecureCoding, NSCopying协议方法

 

进入该属性类型NSJSONReadingOptions可以看到是下图这么定义的

• NSJSONReadingMutableContainers：返回是可变容器类型如NSMutableArray，NSMutableDictionay

• NSJSONReadingMutableLeaves：返回的字符串是NSMutableSting

• NSJSONReadingAllowFragments：json结构最外层可以不是NSArray和NSDictionay

 

接着来看对应的实现文件部分  

三种初始化方法从init方法中可以看到acceptableContentTypes支持"application/json", "text/json", "text/javascript"三种

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error
{
    //response有效性无效
    if (![self validateResponse:(NSHTTPURLResponse *)response data:data error:error]) {
        //无error或者code为NSURLErrorCannotDecodeContentData解析无效，要返回nil
        if (!error || AFErrorOrUnderlyingErrorHasCodeInDomain(*error, NSURLErrorCannotDecodeContentData, AFURLResponseSerializationErrorDomain)) {
            return nil;
        }
    }

    // Workaround for behavior of Rails to return a single space for `head :ok` (a workaround for a bug in Safari), which is not interpreted as valid input by NSJSONSerialization.
    // See https://github.com/rails/rails/issues/1742
    //data由空格字符构成也需要返回nil
    BOOL isSpace = [data isEqualToData:[NSData dataWithBytes:" " length:1]];
    
    if (data.length == 0 || isSpace) {
        return nil;
    }
    
    NSError *serializationError = nil;
    
    id responseObject = [NSJSONSerialization JSONObjectWithData:data options:self.readingOptions error:&serializationError];

    if (!responseObject)
    {
        if (error) {
            *error = AFErrorWithUnderlyingError(serializationError, *error);
        }
        return nil;
    }
    
    if (self.removesKeysWithNullValues) {
        return AFJSONObjectByRemovingKeysWithNullValues(responseObject, self.readingOptions);
    }

    return responseObject;
}

转化和解析方法，这里又出现了两个定义的C函数贴在下面

static BOOL AFErrorOrUnderlyingErrorHasCodeInDomain(NSError *error, NSInteger code, NSString *domain) {
    //error的domain和code与入参对影响等直接返回yes
    if ([error.domain isEqualToString:domain] && error.code == code) {
        return YES;
    } else if (error.userInfo[NSUnderlyingErrorKey]) {//否则判断userInfo中key为NSUnderlyingErrorKey是否有值，有递归调用自身
        return AFErrorOrUnderlyingErrorHasCodeInDomain(error.userInfo[NSUnderlyingErrorKey], code, domain);
    }
    
    return NO;
}

static id AFJSONObjectByRemovingKeysWithNullValues(id JSONObject, NSJSONReadingOptions readingOptions) {
    //数组类
    if ([JSONObject isKindOfClass:[NSArray class]]) {
        //定义可变数组
        NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:[(NSArray *)JSONObject count]];
        for (id value in (NSArray *)JSONObject) {
            //去除NSNull
            [mutableArray addObject:AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions)];
        }

        return (readingOptions & NSJSONReadingMutableContainers) ? mutableArray : [NSArray arrayWithArray:mutableArray];
    } else if ([JSONObject isKindOfClass:[NSDictionary class]]) {//同上
        NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:JSONObject];
        for (id <NSCopying> key in [(NSDictionary *)JSONObject allKeys]) {
            id value = (NSDictionary *)JSONObject[key];
            if (!value || [value isEqual:[NSNull null]]) {
                [mutableDictionary removeObjectForKey:key];
            } else if ([value isKindOfClass:[NSArray class]] || [value isKindOfClass:[NSDictionary class]]) {
                mutableDictionary[key] = AFJSONObjectByRemovingKeysWithNullValues(value, readingOptions);
            }
        }

        return (readingOptions & NSJSONReadingMutableContainers) ? mutableDictionary : [NSDictionary dictionaryWithDictionary:mutableDictionary];
    }

    return JSONObject;
} 

NSSecureCoding, NSCopying协议方法

 

解析XML的子类

不多说比较好理解

 

将JSON转换为PropertyList用到的子类

ContentType支持application/x-plist

 

这里是UIImage的一个分类，从方法名字上看可以想到是一个安全的NSData转Image的方法 

通过NSLock来解决多线程上的一些安全问题

static UIImage * AFImageWithDataAtScale(NSData *data, CGFloat scale) {
    UIImage *image = [UIImage af_safeImageWithData:data];
    if (image.images) {
        return image;
    }
    
    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);

        if (imageRef) {
            CGColorSpaceRef imageColorSpace = CGImageGetColorSpace(imageRef);
            CGColorSpaceModel imageColorSpaceModel = CGColorSpaceGetModel(imageColorSpace);

            // CGImageCreateWithJPEGDataProvider does not properly handle CMKY, so fall back to AFImageWithDataAtScale
            if (imageColorSpaceModel == kCGColorSpaceModelCMYK) {
                CGImageRelease(imageRef);
                imageRef = NULL;
            }
        }
    }

    CGDataProviderRelease(dataProvider);

    UIImage *image = AFImageWithDataAtScale(data, scale);
    if (!imageRef) {
        if (image.images || !image) {
            return image;
        }

        imageRef = CGImageCreateCopy([image CGImage]);
        if (!imageRef) {
            return nil;
        }
    }

    size_t width = CGImageGetWidth(imageRef);
    size_t height = CGImageGetHeight(imageRef);
    size_t bitsPerComponent = CGImageGetBitsPerComponent(imageRef);

    if (width * height > 1024 * 1024 || bitsPerComponent > 8) {
        CGImageRelease(imageRef);

        return image;
    }

    // CGImageGetBytesPerRow() calculates incorrectly in iOS 5.0, so defer to CGBitmapContextCreate
    size_t bytesPerRow = 0;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGColorSpaceModel colorSpaceModel = CGColorSpaceGetModel(colorSpace);
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);

    if (colorSpaceModel == kCGColorSpaceModelRGB) {
        uint32_t alpha = (bitmapInfo & kCGBitmapAlphaInfoMask);
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wassign-enum"
        if (alpha == kCGImageAlphaNone) {
            bitmapInfo &= ~kCGBitmapAlphaInfoMask;
            bitmapInfo |= kCGImageAlphaNoneSkipFirst;
        } else if (!(alpha == kCGImageAlphaNoneSkipFirst || alpha == kCGImageAlphaNoneSkipLast)) {
            bitmapInfo &= ~kCGBitmapAlphaInfoMask;
            bitmapInfo |= kCGImageAlphaPremultipliedFirst;
        }
#pragma clang diagnostic pop
    }

    CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo);

    CGColorSpaceRelease(colorSpace);

    if (!context) {
        CGImageRelease(imageRef);

        return image;
    }

    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;
}

上面的这些个方法涉及图形图像和CoreGraphics，不是很懂。。以后再补吧，先把代码贴在这里。

 

 

最后还有个AFCompoundResponseSerializer，也比较简单不常用不多说了

通过该篇记录下之后需要学习的东西

1. CoreGraphics
2. NSError

以上