serial asynchronous calls for each item in an array - objective-c

Question

given an array of objects, I would like to make an asynchronous call for each object, and then not proceed to the next object until the asynchronous call for the previous object completes.
I have this working code:
#import <XCTest/XCTest.h>
#import <ReactiveCocoa/ReactiveCocoa.h>
#import <TRVSMonitor/TRVSMonitor.h>
#interface FSReactiveCocoaArraySignalProcessingTests : XCTestCase{
NSArray *sequence;
}
#end
#implementation FSReactiveCocoaArraySignalProcessingTests
-(void)setUp{
[super setUp];
sequence = #[#"dog", #"cat", #"mouse", #"rabbit", #"wallabee"];
}
-(void)tearDown{
[super tearDown];
}
- (void)test_maybe_using_the_disposable_method_of_creating_a_signal{
TRVSMonitor *monitor = [TRVSMonitor monitor];
RACSignal *resultingSignal = [[sequence.rac_sequence
map:^(NSString *val){
return [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
NSLog(#"returning signal for %#", val);
[[self fakeApiCall:val]
subscribeNext:^(id next){
[subscriber sendNext:next];
}
completed:^{
[subscriber sendCompleted];
}];
return nil;
}];
}]
foldLeftWithStart:[RACSignal empty]
reduce:^RACSignal *(RACSignal *left, RACSignal *right){
return [left
then:^{
return [right doNext:^(RACTuple *tuple){
//real world side effect for processing end of call.
RACTupleUnpack(NSString *val, NSNumber *len) = tuple;
NSLog(#"word %# has %# chars", val, len);
}];
}];
}];
[resultingSignal subscribeCompleted:^{
NSLog(#"FIN!");
[monitor signal];
}];
XCTAssertTrue([monitor waitWithTimeout:10]);
}
//Returns a new signal that returns a RACTuple<NSString *, NSNumber *>
-(RACSignal *)fakeApiCall:(NSString *)val{
return [[RACSignal return:RACTuplePack(val, #(val.length))]
delay:.5];
}
#end
https://gist.github.com/jonnolen/b0e071b8dd202f7ed912
The question: is there a "more reactive" way to accomplish this?