AFNetworking源码探究（十二） —— 数据解析之子类中协议方法的实现

原创

conanma

修改于 2021-09-03 17:58:23

4910

修改于 2021-09-03 17:58:23

文章被收录于专栏：正则正则

回顾

上一篇讲述了一个AFURLResponseSerialization协议以及AFHTTPResponseSerializer和AFJSONResponseSerializer类中父类那个协议方法的实现。这一篇看一下剩下的那四个子类中该协议的实现。

AFXMLParserResponseSerializer

我们看一下协议的实现

- (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];
}

这个很简单了吧，首先验证有效性，无效的话返回nil，有效的话利用下面的方法返回对象。

[[NSXMLParser alloc] initWithData:data];

AFXMLDocumentResponseSerializer

我们看一下协议的实现

- (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;
}

下面我们就看一下实现过程：

首先判断是否有效，无效的话，return nil
如果有效那么就用下面方法进行实例化对象

NSXMLDocument *document = [[NSXMLDocument alloc] initWithData:data options:self.options error:&serializationError];

如果有错误，调用方法合成error对象

AFPropertyListResponseSerializer

我们看一下协议的实现

- (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;
}

这个的实现过程和上面的是类似的，唯一不同的就是验证有效，实例化调用的方法不一样，这里是

responseObject = [NSPropertyListSerialization propertyListWithData:data options:self.readOptions format:NULL error:&serializationError];

AFImageResponseSerializer

我们看一下协议的实现

- (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 TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_WATCH
    if (self.automaticallyInflatesResponseImage) {
        return AFInflatedImageFromResponseWithDataAtScale((NSHTTPURLResponse *)response, data, self.imageScale);
    } else {
        return AFImageWithDataAtScale(data, self.imageScale);
    }
#else
    // 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;
}

这里我们可以看到：

首先进行的是有效性的验证，无效的话返回nil。
然后利用属性automaticallyInflatesResponseImage进行判断逻辑的执行。

/**
 Whether to automatically inflate response image data for compressed formats (such as PNG or JPEG). Enabling this can significantly improve drawing performance on iOS when used with `setCompletionBlockWithSuccess:failure:`, as it allows a bitmap representation to be constructed in the background rather than on the main thread. `YES` by default.
 */
@property (nonatomic, assign) BOOL automaticallyInflatesResponseImage;

是否自动为压缩格式（如PNG或JPEG）膨胀响应图像数据。如果与setCompletionBlockWithSuccess：failure：一起使用，启用它可以显着提高iOS上的绘图性能，因为它允许在后台而不是在主线程中构建位图表示。默认为YES。

如果可以膨胀，调用下面函数，返回UIImage对象并return。

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;
}
#endif

如果不可以膨胀，那么调用下面的函数返回UIImage对象。

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];
}

AFCompoundResponseSerializer

下面看一下协议在该类中的实现

- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error
{
    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];
}

这里要遍历数组

/**
 The component response serializers.
 */
@property (readonly, nonatomic, copy) NSArray <id<AFURLResponseSerialization>> *responseSerializers;

这个数组中的元素都是遵守AFURLResponseSerialization协议的。然后进行判断如果类型不是AFHTTPResponseSerializer，那么就continue跳出本次循环，继续进行下次的遍历。

如果类型是AFHTTPResponseSerializer，就利用下面方法进行实例化并返回。

id responseObject = [serializer responseObjectForResponse:response data:data error:&serializerError];

后记

本篇主要讲述剩下的五个子类中协议方法的实现。

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

ios

原创声明：本文系作者授权腾讯云开发者社区发表，未经许可，不得转载。

如有侵权，请联系 cloudcommunity@tencent.com 删除。

ios

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