RACStream 、RACSignal 、RACSequence
typedef RACSequence * _Nullable (^RACSequenceBindBlock)(ValueType _Nullable value, BOOL *stop);
typedef RACSignal * _Nullable (^RACSignalBindBlock)(ValueType _Nullable value, BOOL *stop);
typedef RACStream * _Nullable (^RACStreamBindBlock)(ValueType _Nullable value, BOOL *stop);
在实现体中，其实是
//我们就可以使用泛型和__kindof来解决这个问题。 RACStream或者RACStream的子类
- (__kindof RACStream *)bind:(RACStreamBindBlock (^)(void))block;
- (__kindof RACStream *)concat:(RACStream *)stream;
- (__kindof RACStream *)zipWith:(RACStream *)stream;
- (__kindof RACStream *)flattenMap:(__kindof RACStream * _Nullable (^)(ValueType _Nullable value))block;
- (__kindof RACStream *)flatten;
- (__kindof RACStream *)map:(id _Nullable (^)(ValueType _Nullable value))block;
- (__kindof RACStream *)mapReplace:(nullable id)object;
- (__kindof RACStream<ValueType> *)filter:(BOOL (^)(ValueType _Nullable value))block;
- (__kindof RACStream<ValueType> *)ignore:(nullable ValueType)value;
- (__kindof RACStream *)reduceEach:(id _Nullable (^)())reduceBlock;
- (__kindof RACStream<ValueType> *)startWith:(nullable ValueType)value;
- (__kindof RACStream<ValueType> *)skip:(NSUInteger)skipCount;
- (__kindof RACStream<ValueType> *)take:(NSUInteger)count;
- (__kindof RACStream *)scanWithStart:(nullable id)startingValue reduce:(id _Nullable (^)(id _Nullable running, ValueType _Nullable next))reduceBlock;
- (__kindof RACStream *)scanWithStart:(nullable id)startingValue reduceWithIndex:(id _Nullable (^)(id _Nullable running, ValueType _Nullable next, NSUInteger index))reduceBlock;
- (__kindof RACStream *)combinePreviousWithStart:(nullable ValueType)start reduce:(id _Nullable (^)(ValueType _Nullable previous, ValueType _Nullable current))reduceBlock;
- (__kindof RACStream<ValueType> *)takeUntilBlock:(BOOL (^)(ValueType _Nullable x))predicate;
- (__kindof RACStream<ValueType> *)takeWhileBlock:(BOOL (^)(ValueType _Nullable x))predicate;
- (__kindof RACStream<ValueType> *)skipUntilBlock:(BOOL (^)(ValueType _Nullable x))predicate;
- (__kindof RACStream<ValueType> *)skipWhileBlock:(BOOL (^)(ValueType _Nullable x))predicate;
- (__kindof RACStream<ValueType> *)distinctUntilChanged;
- (__kindof RACStream *)empty {
- (__kindof RACStream *)return:(id)value {
- (__kindof RACStream *)join:(id<NSFastEnumeration>)streams block:(RACStream * (^)(id, id))block {
- (__kindof RACStream *)zip:(id<NSFastEnumeration>)streams {
- (__kindof RACStream *)zip:(id<NSFastEnumeration>)streams reduce:(id (^)())reduceBlock {
- (__kindof RACStream *)concat:(id<NSFastEnumeration>)streams {
- (RACSignal<RACTuple *> *)combineLatest:(id<NSFastEnumeration>)signals RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)combineLatest:(id<NSFastEnumeration>)signals reduce:(ValueType _Nullable (^)())reduceBlock RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)merge:(id<NSFastEnumeration>)signals RAC_WARN_UNUSED_RESULT;
- (RACSignal<NSDate *> *)interval:(NSTimeInterval)interval onScheduler:(RACScheduler *)scheduler RAC_WARN_UNUSED_RESULT;
- (RACSignal<NSDate *> *)interval:(NSTimeInterval)interval onScheduler:(RACScheduler *)scheduler withLeeway:(NSTimeInterval)leeway RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)try:(nullable ValueType (^)(NSError **errorPtr))tryBlock RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)defer:(RACSignal<ValueType> * (^)(void))block RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)switch:(RACSignal *)signal cases:(NSDictionary *)cases default:(nullable RACSignal *)defaultSignal RAC_WARN_UNUSED_RESULT;
- (RACSignal<ValueType> *)if:(RACSignal<NSNumber *> *)boolSignal then:(RACSignal *)trueSignal else:(RACSignal *)falseSignal RAC_WARN_UNUSED_RESULT;
