SDWebImage/Docs/SDWebImage-5.0-Migration-guide.md

SDWebImage 5.0 Migration Guide

SDWebImage 5.0 is the latest major release of SDWebImage, a top library for downloading and caching images. As a major release, following Semantic Versioning conventions, 5.0 introduces several API-breaking changes with its new architecture.

This guide is provided in order to ease the transition of existing applications using SDWebImage 4.X to the latest APIs, as well as explain the design and structure of new and changed functionality.

Requirements: iOS 8, Mac OS X 10.10, watchOS 2, tvOS 9, Xcode 9

SDWebImage 5.0 officially supports iOS 8 and later, Mac OS X 10.10 and later, watchOS 2 and later and tvOS 9 and later. It needs Xcode 9 or later to be able to build everything properly.

For targeting previous versions of the SDKs, check README - Backwards compatibility.

Migration

Using the view categories brings no change from 4.x to 5.0.

Objective-C:

[imageView sd_setImageWithURL:url placeholderImage:placeholderImage];

Swift:

imageView.sd_setImage(with: url, placeholderImage: placeholder)

However, all view categories in 5.0 introduce a new extra arg called SDWebImageContext. This param can hold anything, as opposed to the previous SDWebImageOptions enum limitations. This gives developers advanced control for the behavior of image loading (cache, loader, etc). See the declaration for SDWebImageContext for detailed information.

New Feature

Animated Image View

In 5.0, we introduced a brand new mechanism for supporting animated images. This includes animated image loading, rendering, decoding, and also supports customizations (for advanced users).

This animated image solution is available for iOS/tvOS/macOS. The SDAnimatedImage is subclass of UIImage/NSImage, and SDAnimatedImageView is subclass of UIImageView/NSImageView, to make them compatible with the common frameworks APIs. See Animated Image for more detailed information.

Image Transformer

In 5.0, we introduced an easy way to hook an image transformation process after the image was downloaded from network. This allows the user to easily scale, rotate, add rounded corner the original image and even chain a list of transformations. These transformed images will also be stored to the cache as they are after transformation. The reasons for this decision are: avoiding redoing the transformations (which can lead to unwanted behavior) and also time saving. See Image Transformer for more detailed information.

Customization

In 5.0, we refactored our framework architecture in many aspects. This makes our framework easier to customize for advanced users, without the need for hooking anything or forking. We introduced Custom Cache to control detailed cache loading behavior, and separate the memory cache & disk cache implementation. We introduced Custom Loader to allow custom loading from your own source (doesn't have to be the network). And also, we changed the current Custom Coder to work better for custom image decoder/encoder and animated images.

View Indicator

In 5.0, we refactored the image loading indicator API into a better and extensible API for iOS/tvOS/macOS. This is suitable for easy usage like providing a loading view during the image loading process. See View Indicator for more detailed information.

FLAnimatedImage support moved to a dedicated plugin repo

In order to clean up things and make our core project do less things, we decided that the FLAnimatedImage integration does not belong here. From 5.0, this will still be available, but under a dedicated repo SDWebImageFLPlugin.

Photos Plugin

By taking the advantage of the Custom Loader feature, we introduced a plugin to allow easy loading images from the Photos Library. See SDWebImagePhotosPlugin for more detailed information.

Notable Behavior Changes (without API breaking)

Cache

Cache Paths

SDImageCache in 5.x, use ~/Library/Caches/com.hackemist.SDImageCache/default/ as default cache path. However, 4.x use ~/Library/Caches/default/com.hackemist.SDWebImageCache.default/. And don't be worried, we will do the migration automatically once the shared cache initialized.

However, if you have some other custom namespace cache instance, you should try to do migration by yourself. But typically, since the cache is designed to be invalid at any time, you'd better not to bind some important logic related on that cache path changes.

And, if you're previously using any version from 5.0.0-beta to 5.0.0-beta3, please note that the cache folder has been temporarily moved to ~/Library/Caches/default/com.hackemist.SDImageCache.default/, however, the final release version of 5.0.0 use the path above. If you upgrade from those beta version, you may need manually do migration, check +[SDDiskCache moveCacheDirectoryFromPath:toPath:] for detail information.

Cache Cost Function

SDImageCacheConfig.maxMemoryCost can be used to specify the memory cost limit. In the 4.x, the cost function is the pixel count of images. However, 5.x change it into the total bytes size of images.

Because for memory cache, we actually care about the memory usage about bytes, but not the count of pixels. And pixel count can not accurately represent the memory usage.

The bytes of a image occupied in the memory, can use the simple formula below:

bytes size = pixel count * bytes per pixel

The bytes per pixel is a constant depends on image pixel format. For mostly used images (8 bits per channel with alpha), the value is 4. So you can simply migrate your previous pixel count value with 4 multiplied.

Prefetcher

SDWebImagePrefetcher in 5.x, change the concept of fetching batch of URLs. Now, each time you call prefetchURLs:, you will get a token which represents the specified URLs list. It does not cancel the previous URLs which is prefetching, which make the shared prefetcher behaves more intuitively.

However, in 4.x, each time you call prefetchURLs:, it will cancel all previous URLs which is been prefetching.

If you still want the same behavior, manually call cancelPrefetching each time before any prefetchURLs: calls.

• Objective-C

SDWebImagePrefetcher *prefetcher = SDWebImagePrefetcher.sharedImagePrefetcher;
[prefetcher cancelPrefetching];
[prefetcher prefetchURLs:@[url1, url2]];

• Swift

let prefetcher = SDWebImagePrefetcher.shared
prefetcher.cancelPrefetching()
prefetcher.prefetchURLs([url1, url2])

Error codes and domain

For image loading from network, if you don't pass SDWebImageRetryFailed option, we'll try to blocking some URLs which is indeed mark as failed.

This check is done previously in a hard-coded logic for specify error codes. However, due to some compatible issue, we don't check the error domain. (Learn about NSError's domain and codes) And arbitrarily block some codes which may from custom download operation implementations.

Since in 5.x, we supports custom loaders which can use any third-party SDKs, and have their own error domain and error codes. So we now only filter the error codes in NSURLErrorDomain. If you have already using some error codes without error domain check, or you use Custom Download Operation, be sure to update it with the right way.

At the same time, our framework errors, now using the formal SDWebImageErrorDomain with the pre-defined codes. Check SDWebImageError.h for details.

API Changes

SDImageCache

• moved maxMemoryCost and maxMemoryCountLimit to SDImageCacheConfig
• makeDiskCachePath: removed, use NSSearchPathForDirectoriesInDomains with NSString's Path API instead.
• addReadOnlyCachePath: removed, use additionalCachePathBlock instead
• cachePathForKey:inPath: removed, use cachePathForKey: with NSString's path API instead.
• defaultCachePathForKey: removed, use cachePathForKey: instead
• SDCacheQueryCompletedBlock renamed to SDImageCacheQueryCompletionBlock
• SDWebImageCheckCacheCompletionBlock renamed to SDImageCacheCheckCompletionBlock
• SDWebImageCalculateSizeBlock renamed to SDImageCacheCalculateSizeBlock
• getSize renamed to totalDiskSize
• getDiskCount renamed to totalDiskCount

SDImageCacheConfig

• shouldDecompressImages removed. Use SDImageCacheAvoidDecodeImage in cache options instead
• maxCacheAge renamed to maxDiskAge
• maxCacheSize renamed to maxDiskSize

SDWebImageManager

• loadImageWithURL:options:progress:completed: changed the completed param requirement from nullable to nonnull
• loadImageWithURL:options:progress:completed: return type id<SDWebImageOperation> changed to SDWebImageCombinedOperation *
• imageCache changed from nullable to nonnull. And property type changed from SDImageCache * to id<SDImageCache>. The default value does not change.
• imageDownloader renamed to imageLoader and changed from nullable to nonnull. And property type changed from SDWebImageDownloader * to id<SDImageLoader>. The default value does not change.
• cacheKeyFilter property type changed to id<SDWebImageCacheKeyFilter>, you can use +[SDWebImageCacheKeyFilter cacheKeyFilterWithBlock:] to create
• cacheSerializer property type changed to id<SDWebImageCacheSerializer>, you can use +[SDWebImageCacheSerializer cacheSerializerWithBlock:] to create
• SDWebImageCacheKeyFilterBlock's url arg change from nullable to nonnull
• initWithCache:downloader: 's cache arg type changed from SDImageCache * to id<SDImageCache>
• initWithCache:downloader renamed to initWithCache:loader:
• saveImageToCache:forURL: removed. Use SDImageCache storeImage:imageData:forKey:cacheType:completion: (or SDImageCache storeImage:forKey:toDisk:completion: if you use default cache class) with cacheKeyForURL: instead.
• diskImageExistsForURL:completion: removed. Use SDImageCache containsImageForKey:cacheType:completion: (or SDImageCache diskImageExistsWithKey:completion: if you use default cache class) with cacheKeyForURL: instead.
• cachedImageExistsForURL:completion removed. Use SDImageCache containsImageForKey:cacheType:completion: (or SDImageCache diskImageExistsWithKey:completion: and SDImageCache imageFromMemoryCacheForKey: if you use default cache class) with cacheKeyForURL: instead.

SDWebImageManagerDelegate

• removed imageManager:transformDownloadedImage:forKey:, use SDImageTransformer with context option instead

UIView and subclasses (UIImageView, UIButton, ...)

• sd_internalSetImageWithURL:placeholderImage:options:operationKey:setImageBlock:progress:completed: renamed to UIView sd_internalSetImageWithURL:placeholderImage:options:context:setImageBlock:progress:completed: (The biggest changes is that the completion block type from SDExternalCompletionBlock to SDInternalCompletionBlock. Which allow advanced user to get more information of image loading process)
• sd_internalSetImageWithURL:placeholderImage:options:operationKey:setImageBlock:progress:completed:context: removed
• activity indicator refactoring - use sd_imageIndicator with SDWebImageActivityIndicator
  • sd_setShowActivityIndicatorView: removed
  • sd_setIndicatorStyle: removed
  • sd_showActivityIndicatorView removed
  • sd_addActivityIndicator: removed
  • sd_removeActivityIndicator: removed

UIImage

• Renamed isGIF to sd_isAnimated, also NSImage isGIF renamed to NSImage sd_isAnimated
• Renamed decodedImageWithImage: to sd_decodedImageWithImage:
• Renamed decodedAndScaledDownImageWithImage: to sd_decodedAndScaledDownImageWithImage:
• Renamed sd_animatedGIFWithData to sd_imageWithGIFData:
• Removed sd_webpLoopCount

UIImageView

• Removed sd_setImageWithPreviousCachedImageWithURL:placeholderImage:options:progress:completed

SDWebImageDownloader

• shouldDecompressImages moved to SDWebImageDownloaderConfig.shouldDecompressImages
• maxConcurrentDownloads moved to SDWebImageDownloaderConfig.maxConcurrentDownloads
• downloadTimeout moved to SDWebImageDownloaderConfig.downloadTimeout
• operationClass moved to SDWebImageDownloaderConfig.operationClass
• executionOrder moved to SDWebImageDownloaderConfig.executionOrder
• urlCredential moved to SDWebImageDownloaderConfig.urlCredential
• username moved to SDWebImageDownloaderConfig.username
• password moved to SDWebImageDownloaderConfig.password
• initWithSessionConfiguration: removed, use initWithConfig: with session configuration instead
• createNewSessionWithConfiguration: removed, use initWithConfig: with new session configuration instead. To modify shared downloader configuration, provide custom SDWebImageDownloaderConfig.defaultDownloaderConfig before it created.
• headersFilter removed, use requestModifier instead
• cancel: removed, use -[SDWebImageDownloadToken cancel] instead
• shouldDecompressImages removed. Use SDWebImageDownloaderAvoidDecodeImage in downloader options instead
• use SDImageLoaderProgressBlock instead of SDWebImageDownloaderProgressBlock
• use SDImageLoaderCompletedBlock instead of SDWebImageDownloaderCompletedBlock

SDWebImageDownloaderOperation

• initWithRequest:inSession:options:context: is now the designated initializer
• Removed shouldUseCredentialStorage property
• SDWebImageDownloadOperationInterface protocol renamed to SDWebImageDownloadOperation
• expectedSize removed, use response.expectedContentLength instead
• shouldDecompressImages removed. Use SDWebImageDownloaderAvoidDecodeImage in downloader options instead.
• response property change to readonly

SDWebImagePrefetcher

• prefetchURLs: and prefetchURLs:progress:completed: return types changed from void to SDWebImagePrefetchToken
• prefetcherQueue property renamed to delegateQueue
• maxConcurrentDownloads replaced with maxConcurrentPrefetchCount

SDImageCoder

• SDCGColorSpaceGetDeviceRGB() moved to +[SDImageCoderHelper colorSpaceGetDeviceRGB]
• SDCGImageRefContainsAlpha(), moved to +[SDImageCoderHelper imageRefContainsAlpha:]
• decodedImageWithData: replaced with decodedImageWithData:options:
• encodedDataWithImage:format: replaced with encodedDataWithImage:format:options
• init method from SDWebImageProgressiveCoder changed to initIncrementalWithOptions:
• incrementalDecodedImageWithData:finished replaced with updateIncrementalData:finished and incrementalDecodedImageWithOptions: two APIs
• removed decompressedImage:data:options, use +[SDImageCoderHelper decodedImageWithImage:] and +[SDImageCoderHelper decodedAndScaledDownImageWithImage:limitBytes:] instead

Constants

• SDWebImageInternalSetImageGroupKey renamed to SDWebImageContextSetImageGroup
• SDWebImageExternalCustomManagerKey renamed to SDWebImageContextCustomManager

Swift Specific API Change

In SDWebImage 5.0 we did a clean up of the API. We are using many modern Objective-C declarations to generate the Swift API. We now provide full nullability support, string enum, class property, and even custom Swift API name, all to make the framework easier to use for our Swift users. Here are the API change specify for Swift.

UIView+WebCache

• sd_imageURL() changed to sd_imageURL

SDImageCache

• shared() changed to shared

SDWebImageManager

• shared() changed to shared
• isRunning() changed to isRunning

SDWebImageDownloader

• shared() changed to shared
• setOperationClass(_:) available for Swift user with operationClass property
• setSuspended(_:) changed to isSuspended property

SDWebImageDownloadOperation

• SDWebImageDownloadOperationInterface protocol renamed to SDWebImageDownloadOperationProtocol.

SDImageCodersManager

• sharedInstance() changed to shared

SDImageIOCoder

• shared() changed to shared

SDImageGIFCoder

• shared() changed to shared

SDImageWebPCoder

• shared() changed to shared

NSData-ImageContentType

• sd_UTTypeFromSDImageFormat return CFString instead of Unmanaged<CFString>

UIButton-WebCache

• sd_currentImageURL() changed to sd_currentImageURL

NSButton-WebCache

• sd_currentImageURL() changed to sd_currentImageURL
• sd_currentAlternateImageURL() changed to sd_currentAlternateImageURL

Full API Diff

For advanced user who need the detailed API diff, we provide the full diff in a HTML web page (Currently based on 4.4.4 and 5.0.0-beta4):

SDWebImage 5.0 API Diff.