RACSignal: Signal is never invoked - objective-c

Question

I have the following code which is invoked by another signal:
- (RACSignal *)uploadFormItemAttachment_SO:(MyManagedAttachment *)attachment attachmentHeader:(MyFormItemAttachmentHeader*) attachmentHeader
{
RACSignal* signal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
// Code omitted for brevity
// NSDictionary* parameters = #{ #"parameter1" : param1_value};
AFHTTPRequestOperation* operation = [self.requestOperationManager POST:#"UploadForm" parameters:parameters constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
[formData appendPartWithFileURL:fileURL
name:#"content"
error:nil];
} success:^(AFHTTPRequestOperation *operation, id responseObject) {
[self logRequest:operation response:responseObject];
BOOL success = [responseObject[#"success"] boolValue];
if (success)
{
attachment.status = #(AttachmentStatusSent);
[attachment.managedObjectContext MR_saveToPersistentStoreAndWait];
[subscriber sendNext:#(success)];
[subscriber sendCompleted];
}
else
{
NSDictionary* userInfo = nil;
NSString* message = responseObject[#"message"];
if (message != nil && ![message isEqual:[NSNull null]])
{
userInfo = #{ NSLocalizedDescriptionKey : message };
}
else
{
userInfo = #{ NSLocalizedDescriptionKey : [NSString stringWithFormat:#"Error uploading image: %#", filename]};
}
NSError* error = [NSError errorWithDomain:SEFSAPIClientErrorDomain code:1100 userInfo:userInfo];
[subscriber sendError:error];
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[self logRequest:operation error:error];
[subscriber sendError:error];
}];
[self.requestOperationManager.operationQueue addOperation:operation];
return [RACDisposable disposableWithBlock:^{
[operation cancel];
}];
}];
return signal;
}
My problem is that the signal object is never invoked and the code never runs. It goes straight into the last statement
return signal;
and the code inside the signal never gets executed. Could anyone help please?
I have tried adding a [subscriber sendNext: signal] at the end of the RACSignal definition but it makes no difference.
The previous method is called by this one below:
- (RACSignal *)uploadPendingAttachments_SO
{
NSArray *pendingAttachments = [MyManagedAttachment MR_findAllWithPredicate:[NSPredicate predicateWithFormat:#"status == %ld && form.status == %ld", MyAttachmentStatusPending, SEFSFormStatusUploadedForm]
inContext:[NSManagedObjectContext MR_defaultContext]];
RACSignal* batchSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
[pendingAttachments enumerateObjectsUsingBlock:^(MyManagedAttachment* pendingImage, NSUInteger idx, BOOL *stop) {
// Check if we have a top list item id which indicates form data has been created on the back-end SharePoint server.
NSString* siteID = pendingImage.siteID;
NSString* formID = pendingImage.formID;
NSManagedObjectContext* context = [NSManagedObjectContext MR_contextWithParent:[NSManagedObjectContext MR_defaultContext]];
NSPredicate* predicate = [NSPredicate predicateWithFormat:#"projectID = %# AND formID = %#", siteID, formID];
MyManagedForm* form = [MyManagedForm MR_findFirstWithPredicate:predicate
inContext:context];
if (form.topListItemID && pendingImage.formItemID) {
NSString* listName = pendingImage.list;
RACSignal* getFormItemAttachmentHeadersSignal = [[self getFormItemAttachmentHeaders:listName
topListItemID:form.topListItemID
form:form
] map:^id(NSMutableArray* value) {
NSArray* attachmentHeaders = [value copy];
RACSignal* attachmentsBatchSignal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
[attachmentHeaders enumerateObjectsUsingBlock:^(MyFormItemAttachmentHeader* attachmentHeader, NSUInteger idx, BOOL *stop)
{
// Look for the local attachment using attachment header from server
NSPredicate* predicate = [NSPredicate predicateWithFormat:#"identifier = %#", attachmentHeader.document];
NSArray* foundAttachment = [pendingAttachments filteredArrayUsingPredicate:predicate];
MyManagedAttachment* fullAttachment = foundAttachment[0];
NSString* listName = pendingImage.list;
RACSignal* uploadFormItemAttachmentSignal = [[self uploadFormItemAttachment_SO:fullAttachment
attachmentHeader:attachmentHeader ] map:^id(id value) {
BOOL success = [value boolValue];
return nil;
}];
[subscriber sendNext:uploadFormItemAttachmentSignal];
}];
[subscriber sendCompleted];
return nil;
}];
return attachmentsBatchSignal; // check this
}];
[subscriber sendNext:getFormItemAttachmentHeadersSignal];
}
else {
RACSignal* uploadFormSignal = [[self uploadAttachment:pendingImage] map:^id(NSNumber* value) {
NSMutableArray* valuesArray = [NSMutableArray array];
[valuesArray addObject:value];
[valuesArray addObject:pendingImage.objectID];
RACTuple* tuple = [RACTuple tupleWithObjectsFromArray:valuesArray
convertNullsToNils:YES];
return tuple;
}];
[subscriber sendNext:uploadFormSignal];
}
}];
[subscriber sendCompleted];
return nil;
}];
return [batchSignal flatten:2];
}