Hide RACCommand's subscriber behavior in a private RACSubject

Fixes ReactiveCocoa#373.

ReactiveCocoaFramework/ReactiveCocoa/RACCommand.h

@@ -7,13 +7,13 @@
 //
 
 #import <Foundation/Foundation.h>
-#import <ReactiveCocoa/RACSubject.h>
+#import <ReactiveCocoa/RACSignal.h>
 
 // A command is a signal triggered in response to some action, typically
 // UI-related.
 //
 // Each `next` sent by a RACCommand corresponds to a value passed to -execute:.
-@interface RACCommand : RACSubject
+@interface RACCommand : RACSignal
 
 // Whether or not this command can currently execute.
 //
@@ -95,3 +95,13 @@
 - (BOOL)execute:(id)value;
 
 @end
+
+@interface RACCommand (Deprecated)
+
+- (void)sendNext:(id)value __attribute__((deprecated("Commands should not be manually controlled")));
+- (void)sendError:(NSError *)error __attribute__((deprecated("Commands should not be manually controlled")));
+- (void)sendCompleted __attribute__((deprecated("Commands should not be manually controlled")));
+- (void)didSubscribeWithDisposable:(RACDisposable *)disposable __attribute__((deprecated("Commands should not be manually controlled")));
++ (instancetype)subject __attribute__((deprecated("Use +command instead")));
+
+@end

ReactiveCocoaFramework/ReactiveCocoa/RACCommand.m

@@ -10,6 +10,7 @@
 #import "EXTScope.h"
 #import "RACScheduler.h"
 #import "RACSignal+Operations.h"
+#import "RACSubject.h"
 #import "RACSubscriptingAssignmentTrampoline.h"
 #import <libkern/OSAtomic.h>
 
@@ -25,6 +26,11 @@ @interface RACCommand () {
 
 @property (atomic, readwrite) BOOL canExecute;
 
+// A signal of the values passed to -execute:.
+//
+// Subscriptions to the receiver will actually be redirected to this subject.
+@property (nonatomic, strong, readonly) RACSubject *values;
+
 // Improves the performance of KVO on the receiver.
 //
 // See the documentation for <NSKeyValueObserving> for more information.
@@ -63,6 +69,14 @@ - (void)decrementItemsInFlight {
 	[self didChangeValueForKey:@keypath(self.executing)];
 }
 
+- (NSString *)name {
+	return self.values.name;
+}
+
+- (void)setName:(NSString *)name {
+	self.values.name = name;
+}
+
 #pragma mark Lifecycle
 
 + (instancetype)command {
@@ -81,6 +95,7 @@ - (id)initWithCanExecuteSignal:(RACSignal *)canExecuteSignal {
 	self = [super init];
 	if (self == nil) return nil;
 
+	_values = [RACSubject subject];
 	_errors = [RACSubject subject];
 
 	RAC(self.canExecute) = [RACSignal
@@ -103,7 +118,7 @@ - (RACSignal *)addSignalBlock:(RACSignal * (^)(id value))signalBlock {
 
 	@weakify(self);
 
-	return [[[[self
+	return [[[[self.values
 		doNext:^(id _) {
 			@strongify(self);
 			[self incrementItemsInFlight];
@@ -138,12 +153,18 @@ - (BOOL)execute:(id)value {
 		[self incrementItemsInFlight];
 	}
 
-	[self sendNext:value];
+	[self.values sendNext:value];
 	[self decrementItemsInFlight];
 
 	return YES;
 }
 
+#pragma mark RACSignal
+
+- (RACDisposable *)subscribe:(id<RACSubscriber>)subscriber {
+	return [self.values subscribe:subscriber];
+}
+
 #pragma mark NSKeyValueObserving
 
 + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)key {
@@ -154,3 +175,32 @@ + (BOOL)automaticallyNotifiesObserversForKey:(NSString *)key {
 }
 
 @end
+
+@implementation RACCommand (Deprecated)
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-implementations"
+
+- (void)sendNext:(id)value {
+	[self.values sendNext:value];
+}
+
+- (void)sendError:(NSError *)error {
+	[self.values sendError:error];
+}
+
+- (void)sendCompleted {
+	[self.values sendCompleted];
+}
+
+- (void)didSubscribeWithDisposable:(RACDisposable *)disposable {
+	[self.values didSubscribeWithDisposable:disposable];
+}
+
++ (instancetype)subject {
+	return [self command];
+}
+
+#pragma clang diagnostic pop
+
+@end

ReactiveCocoaFramework/ReactiveCocoaTests/RACCommandSpec.m

@@ -11,6 +11,7 @@
 #import "RACScheduler.h"
 #import "RACSequence.h"
 #import "RACSignal+Operations.h"
+#import "RACSubject.h"
 #import "RACUnit.h"
 
 SpecBegin(RACCommand)