Supports the user to customize the default disk cache directory, which can be used to share cache for App && App Extension

SDWebImage/Core/SDImageCache.h

@@ -103,6 +103,15 @@ typedef NS_OPTIONS(NSUInteger, SDImageCacheOptions) {
  */
 @property (nonatomic, class, readonly, nonnull) SDImageCache *sharedImageCache;
 
+/**
+ * Control the default disk cache directory. This will effect all the SDImageCache instance created, even for shared image cache.
+ * This can be used to share the same disk cache with the App and App Extension (Today/Notification Widget) using `- [NSFileManager.containerURLForSecurityApplicationGroupIdentifier:]`.
+ * @note If you pass nil, the value will be reset to `~/Library/Caches/com.hackemist.SDImageCache`.
+ * @note We still preserve the `namespace` arg, which means, if you change this property into `/path/to/use`,  the `SDImageCache.sharedImageCache.diskCachePath` should be `/path/to/use/default` because shared image cache use `default` as namespace.
+ * Defaults to nil.
+ */
+@property (nonatomic, class, readwrite, null_resettable) NSString *defaultDiskCacheDirectory;
+
 /**
  * Init a new cache store with a specific namespace
  *

SDWebImage/Core/SDImageCache.m

@@ -15,6 +15,8 @@
 #import "UIImage+Metadata.h"
 #import "UIImage+ExtendedCacheData.h"
 
+static NSString * _defaultDiskCacheDirectory;
+
 @interface SDImageCache ()
 
 #pragma mark - Properties
@@ -40,6 +42,17 @@
     return instance;
 }
 
++ (NSString *)defaultDiskCacheDirectory {
+    if (!_defaultDiskCacheDirectory) {
+        _defaultDiskCacheDirectory = [[self userCacheDirectory] stringByAppendingPathComponent:@"com.hackemist.SDImageCache"];
+    }
+    return _defaultDiskCacheDirectory;
+}
+
++ (void)setDefaultDiskCacheDirectory:(NSString *)defaultDiskCacheDirectory {
+    _defaultDiskCacheDirectory = [defaultDiskCacheDirectory copy];
+}
+
 - (instancetype)init {
     return [self initWithNamespace:@"default"];
 }
@@ -75,8 +88,11 @@
         if (directory != nil) {
             _diskCachePath = [directory stringByAppendingPathComponent:ns];
         } else {
-            NSString *path = [[[self userCacheDirectory] stringByAppendingPathComponent:@"com.hackemist.SDImageCache"] stringByAppendingPathComponent:ns];
-            _diskCachePath = path;
+            if (!directory) {
+                // Use default disk cache directory
+                directory = [self.class defaultDiskCacheDirectory];
+            }
+            _diskCachePath = [directory stringByAppendingPathComponent:ns];
         }
         
         NSAssert([config.diskCacheClass conformsToProtocol:@protocol(SDDiskCache)], @"Custom disk cache class must conform to `SDDiskCache` protocol");
@@ -121,7 +137,7 @@
     return [self.diskCache cachePathForKey:key];
 }
 
-- (nullable NSString *)userCacheDirectory {
++ (nullable NSString *)userCacheDirectory {
     NSArray<NSString *> *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
     return paths.firstObject;
 }
@@ -131,9 +147,9 @@
         static dispatch_once_t onceToken;
         dispatch_once(&onceToken, ^{
             // ~/Library/Caches/com.hackemist.SDImageCache/default/
-            NSString *newDefaultPath = [[[self userCacheDirectory] stringByAppendingPathComponent:@"com.hackemist.SDImageCache"] stringByAppendingPathComponent:@"default"];
+            NSString *newDefaultPath = [[[self.class userCacheDirectory] stringByAppendingPathComponent:@"com.hackemist.SDImageCache"] stringByAppendingPathComponent:@"default"];
             // ~/Library/Caches/default/com.hackemist.SDWebImageCache.default/
-            NSString *oldDefaultPath = [[[self userCacheDirectory] stringByAppendingPathComponent:@"default"] stringByAppendingPathComponent:@"com.hackemist.SDWebImageCache.default"];
+            NSString *oldDefaultPath = [[[self.class userCacheDirectory] stringByAppendingPathComponent:@"default"] stringByAppendingPathComponent:@"com.hackemist.SDWebImageCache.default"];
             dispatch_async(self.ioQueue, ^{
                 [((SDDiskCache *)self.diskCache) moveCacheDirectoryFromPath:oldDefaultPath toPath:newDefaultPath];
             });