Making AFImageCache lazy init thread safe since it is called from main thread and background threads. Also making the increment and decrement for AFNetworkActivityIndicatorManager thread safe since start/stopAnimating are called from different threads.

AFNetworking/AFImageCache.m

@@ -30,10 +30,11 @@ static inline NSString * AFImageCacheKey(NSURLRequest *urlRequest, CGSize imageS
 
 + (id)sharedImageCache {
     static NSCache *_sharedImageCache = nil;
-    
-    if (!_sharedImageCache) {
+    static dispatch_once_t oncePredicate;
+
+    dispatch_once(&oncePredicate, ^{
         _sharedImageCache = [[self alloc] init];
-    }
+    });
     
     return _sharedImageCache;
 }

AFNetworking/AFNetworkActivityIndicatorManager.m

@@ -31,19 +31,22 @@
 
 + (AFNetworkActivityIndicatorManager *)sharedManager {
     static AFNetworkActivityIndicatorManager *_sharedManager = nil;
-    if (!_sharedManager) {
+    static dispatch_once_t oncePredicate;
+    dispatch_once(&oncePredicate, ^{
         _sharedManager = [[AFNetworkActivityIndicatorManager alloc] init];
-    }
+    });
     
     return _sharedManager;
 }
 
 - (void)setActivityCount:(NSInteger)activityCount {
-    [self willChangeValueForKey:@"activityCount"];
-    _activityCount = MAX(activityCount, 0);
-    [self didChangeValueForKey:@"activityCount"];
-
-    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:self.activityCount > 0];
+    @synchronized(self) {
+        [self willChangeValueForKey:@"activityCount"];
+        _activityCount = MAX(activityCount, 0);
+        [self didChangeValueForKey:@"activityCount"];
+        
+        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:self.activityCount > 0];
+    }
 }
 
 - (void)startAnimating {

Example/AFNetworking Example.xcodeproj/project.pbxproj

@@ -10,7 +10,6 @@
 		F85CE2D413EC478F00BFAE01 /* NSString+AFNetworking.m in Sources */ = {isa = PBXBuildFile; fileRef = F85CE2D313EC478F00BFAE01 /* NSString+AFNetworking.m */; };
 		F85CE2DC13EC4A4200BFAE01 /* NSMutableURLRequest+AFNetworking.m in Sources */ = {isa = PBXBuildFile; fileRef = F85CE2DB13EC4A4200BFAE01 /* NSMutableURLRequest+AFNetworking.m */; };
 		F85CE55513EC759200BFAE01 /* NSData+AFNetworking.m in Sources */ = {isa = PBXBuildFile; fileRef = F85CE55413EC759200BFAE01 /* NSData+AFNetworking.m */; };
-		F85CE55B13EC771100BFAE01 /* libz.1.2.5.dylib in Frameworks */ = {isa = PBXBuildFile; fileRef = F85CE55A13EC771100BFAE01 /* libz.1.2.5.dylib */; settings = {ATTRIBUTES = (Weak, ); }; };
 		F874B5D913E0AA6500B28E3E /* AFHTTPRequestOperation.m in Sources */ = {isa = PBXBuildFile; fileRef = F874B5C913E0AA6500B28E3E /* AFHTTPRequestOperation.m */; };
 		F874B5DA13E0AA6500B28E3E /* AFImageCache.m in Sources */ = {isa = PBXBuildFile; fileRef = F874B5CA13E0AA6500B28E3E /* AFImageCache.m */; };
 		F874B5DB13E0AA6500B28E3E /* AFImageRequestOperation.m in Sources */ = {isa = PBXBuildFile; fileRef = F874B5CB13E0AA6500B28E3E /* AFImageRequestOperation.m */; };
@@ -33,6 +32,7 @@
 		F8E469671395739D00DB05C8 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = F8E469661395739D00DB05C8 /* Foundation.framework */; };
 		F8E469691395739D00DB05C8 /* CoreGraphics.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = F8E469681395739D00DB05C8 /* CoreGraphics.framework */; };
 		F8E469DF13957DD500DB05C8 /* CoreLocation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = F8E469DE13957DD500DB05C8 /* CoreLocation.framework */; };
+		FF2B770D140DAC4E00A8DEC2 /* libz.dylib in Frameworks */ = {isa = PBXBuildFile; fileRef = FF2B770C140DAC4E00A8DEC2 /* libz.dylib */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -42,7 +42,6 @@
 		F85CE2DB13EC4A4200BFAE01 /* NSMutableURLRequest+AFNetworking.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = "NSMutableURLRequest+AFNetworking.m"; path = "../AFNetworking/NSMutableURLRequest+AFNetworking.m"; sourceTree = "<group>"; };
 		F85CE55313EC759100BFAE01 /* NSData+AFNetworking.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "NSData+AFNetworking.h"; path = "../AFNetworking/NSData+AFNetworking.h"; sourceTree = "<group>"; };
 		F85CE55413EC759200BFAE01 /* NSData+AFNetworking.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = "NSData+AFNetworking.m"; path = "../AFNetworking/NSData+AFNetworking.m"; sourceTree = "<group>"; };
-		F85CE55A13EC771100BFAE01 /* libz.1.2.5.dylib */ = {isa = PBXFileReference; lastKnownFileType = "compiled.mach-o.dylib"; name = libz.1.2.5.dylib; path = usr/lib/libz.1.2.5.dylib; sourceTree = SDKROOT; };
 		F874B5C913E0AA6500B28E3E /* AFHTTPRequestOperation.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = AFHTTPRequestOperation.m; path = ../AFNetworking/AFHTTPRequestOperation.m; sourceTree = "<group>"; };
 		F874B5CA13E0AA6500B28E3E /* AFImageCache.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = AFImageCache.m; path = ../AFNetworking/AFImageCache.m; sourceTree = "<group>"; };
 		F874B5CB13E0AA6500B28E3E /* AFImageRequestOperation.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = AFImageRequestOperation.m; path = ../AFNetworking/AFImageRequestOperation.m; sourceTree = "<group>"; };
@@ -86,6 +85,7 @@
 		F8E469E013957DF100DB05C8 /* Security.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Security.framework; path = System/Library/Frameworks/Security.framework; sourceTree = SDKROOT; };
 		F8E469E213957DF700DB05C8 /* SystemConfiguration.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = SystemConfiguration.framework; path = System/Library/Frameworks/SystemConfiguration.framework; sourceTree = SDKROOT; };
 		F8E469E413957E0400DB05C8 /* SystemConfiguration.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = SystemConfiguration.framework; path = System/Library/Frameworks/SystemConfiguration.framework; sourceTree = SDKROOT; };
+		FF2B770C140DAC4E00A8DEC2 /* libz.dylib */ = {isa = PBXFileReference; lastKnownFileType = "compiled.mach-o.dylib"; name = libz.dylib; path = usr/lib/libz.dylib; sourceTree = SDKROOT; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -93,11 +93,11 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				F85CE55B13EC771100BFAE01 /* libz.1.2.5.dylib in Frameworks */,
 				F8E469651395739D00DB05C8 /* UIKit.framework in Frameworks */,
 				F8E469671395739D00DB05C8 /* Foundation.framework in Frameworks */,
 				F8E469691395739D00DB05C8 /* CoreGraphics.framework in Frameworks */,
 				F8E469DF13957DD500DB05C8 /* CoreLocation.framework in Frameworks */,
+				FF2B770D140DAC4E00A8DEC2 /* libz.dylib in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -194,7 +194,6 @@
 		F8E469631395739D00DB05C8 /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
-				F85CE55A13EC771100BFAE01 /* libz.1.2.5.dylib */,
 				F8E469E413957E0400DB05C8 /* SystemConfiguration.framework */,
 				F8E469E213957DF700DB05C8 /* SystemConfiguration.framework */,
 				F8E469E013957DF100DB05C8 /* Security.framework */,
@@ -202,6 +201,7 @@
 				F8E469641395739D00DB05C8 /* UIKit.framework */,
 				F8E469661395739D00DB05C8 /* Foundation.framework */,
 				F8E469681395739D00DB05C8 /* CoreGraphics.framework */,
+				FF2B770C140DAC4E00A8DEC2 /* libz.dylib */,
 			);
 			name = Frameworks;
 			sourceTree = "<group>";