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.
Using the view categories brings no change from 4.x to 5.0.
[imageView sd_setImageWithURL:url placeholderImage:placeholderImage];
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.
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
SDAnimatedImage is subclass of
SDAnimatedImageView is subclass of
UIImageView/NSImageView, to make them compatible with the common frameworks APIs. See Animated Image for more detailed information.
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.
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.
In 5.0, we refactored the image loading indicator API into a better and extensible API for
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.
Notable Behavior Changes (without API breaking)
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-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.
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
SDWebImagePrefetcher *prefetcher = SDWebImagePrefetcher.sharedImagePrefetcher; [prefetcher cancelPrefetching]; [prefetcher prefetchURLs:@[url1, url2]];
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.
NSSearchPathForDirectoriesInDomainswith NSString’s Path API instead.
cachePathForKey:with NSString’s path API instead.
SDImageCacheAvoidDecodeImagein cache options instead
completedparam requirement from
imageCachechanged from nullable to nonnull. And property type changed from
id<SDImageCache>. The default value does not change.
imageLoaderand changed from nullable to nonnull. And property type changed from
id<SDImageLoader>. The default value does not change.
cacheKeyFilterproperty type changed to
id<SDWebImageCacheKeyFilter>, you can use
+[SDWebImageCacheKeyFilter cacheKeyFilterWithBlock:]to create
cacheSerializerproperty type changed to
id<SDWebImageCacheSerializer>, you can use
+[SDWebImageCacheSerializer cacheSerializerWithBlock:]to create
urlarg change from nullable to nonnull
cachearg type changed from
SDImageCache storeImage:forKey:toDisk:completion:if you use default cache class) with
SDImageCache diskImageExistsWithKey:completion:if you use default cache class) with
SDImageCache imageFromMemoryCacheForKey:if you use default cache class) with
SDImageTransformerwith context option instead
UIView and subclasses (UIImageView, UIButton, …)
UIView sd_internalSetImageWithURL:placeholderImage:options:context:setImageBlock:progress:completed:(The biggest changes is that the completion block type from
SDInternalCompletionBlock. Which allow advanced user to get more information of image loading process)
- activity indicator refactoring - use
NSImage isGIFrenamed to
initWithConfig:with session configuration instead
initWithConfig:with new session configuration instead. To modify shared downloader configuration, provide custom
SDWebImageDownloaderConfig.defaultDownloaderConfigbefore it created.
SDWebImageDownloaderAvoidDecodeImagein downloader options instead
initWithRequest:inSession:options:context:is now the designated initializer
SDWebImageDownloadOperationInterfaceprotocol renamed to
SDWebImageDownloaderAvoidDecodeImagein downloader options instead.
responseproperty change to readonly
prefetchURLs:progress:completed:return types changed from
prefetcherQueueproperty renamed to
SDCGImageRefContainsAlpha(), moved to
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.
setOperationClass(_:)available for Swift user with
SDWebImageDownloadOperationInterfaceprotocol renamed to
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):