Fix to -rac_signalForSelector: properly implement -respondsToSelector: for optional method from a protocol

ReactiveCocoaFramework/ReactiveCocoa/NSObject+RACSelectorSignal.m

@@ -99,12 +99,16 @@ static void RACSwizzleRespondsToSelector(Class class) {
 	// added by -rac_signalForSelector:.
 	//
 	// If the selector has a method defined on the receiver's actual class, and
-	// if that method's implementation is _objc_msgForward, then return YES.
+	// if that method's implementation is _objc_msgForward, then returns whether
+	// the instance has a signal for the selector.
 	// Otherwise, call the original -respondsToSelector:.
 	id newRespondsToSelector = ^ BOOL (id self, SEL selector) {
 		Method method = rac_getImmediateInstanceMethod(object_getClass(self), selector);
 
-		if (method != NULL && method_getImplementation(method) == _objc_msgForward) return YES;
+		if (method != NULL && method_getImplementation(method) == _objc_msgForward) {
+			SEL aliasSelector = RACAliasForSelector(selector);
+			return objc_getAssociatedObject(self, aliasSelector) != nil;
+		}
 
 		return originalRespondsToSelector(self, respondsToSelectorSEL, selector);
 	};
@@ -248,6 +252,7 @@ static Class RACSwizzleClass(NSObject *self) {
 		if (subclass == nil) return nil;
 
 		RACSwizzleForwardInvocation(subclass);
+		RACSwizzleRespondsToSelector(subclass);
 		objc_registerClassPair(subclass);
 	}
 

ReactiveCocoaFramework/ReactiveCocoaTests/NSObjectRACSelectorSignalSpec.m

@@ -190,6 +190,29 @@ - (id)objectValue;
 
 		expect([object respondsToSelector:selector]).to.beTruthy();
 	});
+
+	it(@"should properly implement -respondsToSelector: for optional method from a protocol", ^{
+		// Selector for the targeted optional method from a protocol.
+		SEL selector = @selector(optionalProtocolMethodWithObjectValue:);
+
+		RACTestObject *object1 = [[RACTestObject alloc] init];
+
+		// Method implementation of the selector is added to its swizzled class.
+		[object1 rac_signalForSelector:selector fromProtocol:@protocol(RACTestProtocol)];
+
+		expect([object1 respondsToSelector:selector]).to.beTruthy();
+
+		RACTestObject *object2 = [[RACTestObject alloc] init];
+
+		// Call -rac_signalForSelector: to swizzle this instance's class,
+		// method implementations of -respondsToSelector: and
+		// -forwardInvocation:.
+		[object2 rac_signalForSelector:@selector(lifeIsGood:)];
+
+		// This instance should not respond to the selector because of not
+		// calling -rac_signalForSelector: with the selector.
+		expect([object2 respondsToSelector:selector]).to.beFalsy();
+	});
 
 	it(@"should send non-object arguments", ^{
 		RACTestObject *object = [[RACTestObject alloc] init];

ReactiveCocoaFramework/ReactiveCocoaTests/RACTestObject.h

@@ -13,7 +13,14 @@ typedef struct {
 	double doubleField;
 } RACTestStruct;
 
-@interface RACTestObject : NSObject
+@protocol RACTestProtocol <NSObject>
+
+@optional
+- (void)optionalProtocolMethodWithObjectValue:(id)objectValue;
+
+@end
+
+@interface RACTestObject : NSObject <RACTestProtocol>
 
 @property (nonatomic, strong) id objectValue;
 @property (nonatomic, strong) id secondObjectValue;