前面可以看到RAC中的zip和combineLatest最后都会走到reduceEach，这个RACStream中的方法，来看源码：
- (instancetype)reduceEach:(id (^)())reduceBlock {
NSCParameterAssert(reduceBlock != nil);
__weak RACStream *stream __attribute__((unused)) = self;
return [[self map:^(RACTuple *t) {
NSCAssert([t isKindOfClass:RACTuple.class], @"Value from stream %@ is not a tuple: %@", stream, t);
return [RACBlockTrampoline invokeBlock:reduceBlock withArguments:t];
}] setNameWithFormat:@"[%@] -reduceEach:", self.name];
}
打了断言就是数据类型必须封装为RACTuple，核心代码为RACBlockTrampoline：
//初始化，没啥说的
- (id)initWithBlock:(id)block {
self = [super init];
if (self == nil) return nil;
_block = [block copy];
return self;
}
+ (id)invokeBlock:(id)block withArguments:(RACTuple *)arguments {
NSCParameterAssert(block != NULL);
RACBlockTrampoline *trampoline = [[self alloc] initWithBlock:block];
return [trampoline invokeWithArguments:arguments];
}
- (id)invokeWithArguments:(RACTuple *)arguments {
//根据RACTuple的个数选择selector，最多支持15个，也就是你combineLatest最多只能有15个信号
SEL selector = [self selectorForArgumentCount:arguments.count];
//NSInvocation可以单纯的理解为执行一个方法，比performSelector强大，因为他可以带很多参数进去
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:selector]];
invocation.selector = selector;
invocation.target = self;
for (NSUInteger i = 0; i < arguments.count; i++) {
//把参数带进去
id arg = arguments[i];
NSInteger argIndex = (NSInteger)(i + 2);
[invocation setArgument:&arg atIndex:argIndex];
}
[invocation invoke];
__unsafe_unretained id returnVal;
[invocation getReturnValue:&returnVal];
return returnVal;
}
//写法不漂亮，也是无奈之举
- (SEL)selectorForArgumentCount:(NSUInteger)count {
NSCParameterAssert(count > 0);
switch (count) {
case 0: return NULL;
case 1: return @selector(performWith:);
case 2: return @selector(performWith::);
case 3: return @selector(performWith:::);
case 4: return @selector(performWith::::);
case 5: return @selector(performWith:::::);
case 6: return @selector(performWith::::::);
case 7: return @selector(performWith:::::::);
case 8: return @selector(performWith::::::::);
case 9: return @selector(performWith:::::::::);
case 10: return @selector(performWith::::::::::);
case 11: return @selector(performWith:::::::::::);
case 12: return @selector(performWith::::::::::::);
case 13: return @selector(performWith:::::::::::::);
case 14: return @selector(performWith::::::::::::::);
case 15: return @selector(performWith:::::::::::::::);
}
NSCAssert(NO, @"The argument count is too damn high! Only blocks of up to 15 arguments are currently supported.");
return NULL;
}
- (id)performWith:(id)obj1 {
id (^block)(id) = self.block;
return block(obj1);
}
- (id)performWith:(id)obj1 :(id)obj2 {
id (^block)(id, id) = self.block;
return block(obj1, obj2);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 {
id (^block)(id, id, id) = self.block;
return block(obj1, obj2, obj3);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 {
id (^block)(id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 {
id (^block)(id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 {
id (^block)(id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 {
id (^block)(id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 {
id (^block)(id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 {
id (^block)(id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 {
id (^block)(id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 :(id)obj11 {
id (^block)(id, id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 :(id)obj11 :(id)obj12 {
id (^block)(id, id, id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 :(id)obj11 :(id)obj12 :(id)obj13 {
id (^block)(id, id, id, id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12, obj13);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 :(id)obj11 :(id)obj12 :(id)obj13 :(id)obj14 {
id (^block)(id, id, id, id, id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12, obj13, obj14);
}
- (id)performWith:(id)obj1 :(id)obj2 :(id)obj3 :(id)obj4 :(id)obj5 :(id)obj6 :(id)obj7 :(id)obj8 :(id)obj9 :(id)obj10 :(id)obj11 :(id)obj12 :(id)obj13 :(id)obj14 :(id)obj15 {
id (^block)(id, id, id, id, id, id, id, id, id, id, id, id, id, id, id) = self.block;
return block(obj1, obj2, obj3, obj4, obj5, obj6, obj7, obj8, obj9, obj10, obj11, obj12, obj13, obj14, obj15);
}