ReactiveCocoa is a functional reactive programming framework that provides APIs for composing and transforming streams of values through 'signals'. It aims to simplify programming by minimizing state management and allowing developers to focus on the 'what' rather than the 'how', enabling declarative coding styles. The document illustrates practical examples of using ReactiveCocoa for managing UI interactions and network validations in iOS applications.

1. ReactiveCocoa
Bob Spryn
LoHi Labs
@sprynmr (github, twitter)
!
!
!
https://github.com/ReactiveCocoa/ReactiveCocoa

2. ReactiveCocoa
•
An implementation of functional reactive programming
•
It provides APIs for composing and transforming
streams of values
•
“Signals” send you these values over time for you to
react to
http://en.wikipedia.org/wiki/Functional_reactive_programming

3. ?

4. Not just another API.
It enables you to
Program Smarter
Focus on WHAT not HOW

5. Reactive!!! Declarative!!!
What does that even mean?

6. • Setup
your reactions
• Compose,
Reactive!!! Declarative!!!
split, filter, etc.
What does that even mean?

7. Imperative
The way we normally program.

8. Imperative
The way we normally program.
•
Observe, wait, then command & control
•
Dealing with the HOW, not just the WHAT
•
Code for controlling flow is spread all over

9. Auto-layout : Managing Frames
ReactiveCocoa : Imperative programming

10. Complexity
Is
STATE

11. BOOL loadingNextPageOfComments;
2 states
BOOL commentsAreShowing;
4 states
BOOL commentsLoadingShowing;
8 states
BOOL flippingAnswers;
16 states
BOOL isOwnerOfQuestion;
32 states

12. - (void) updateChangeAnswerButtonText {
if (self.didAnswerQuestion && self.inResultsView) {
[self.commentHeaderCell configureWithStyle:TCQuestionDetailCommentHeaderCellChangeAnswer];
} else if (self.isOwnerOfQuestion && !self.didAnswerQuestion && self.inResultsView) {
[self.commentHeaderCell configureWithStyle:TCQuestionDetailCommentHeaderCellViewAnswers];
} else {
[self.commentHeaderCell configureWithStyle:TCQuestionDetailCommentHeaderCellViewStats];
}
}
- (void) updateViewCommentStatus {
if ((self.didAnswerQuestion || self.isOwnerOfQuestion) && !self.commentsAreShowing) {
self.commentsAreShowing = YES;
- (void) prepareForReuse {
self.commentsLoadingShowing = YES;
self.state = TCQuestionDetailViewContro
…
self.questionFullyLoaded = NO;
}
self.isOwnerOfQuestion = NO;
self.didAnswerQuestion = NO;
[self showCommentBox:self.inResultsView || self.isOwnerOfQuestion];
[self showCommentBox:NO];
}
self.loadingNextPageOfComments = NO;
self.commentsAreShowing = NO;
self.commentsLoadingShowing = NO;
!
^aBlock {
sself.didAnswerQuestion = sself.question.userResponse ? YES : NO;
sself.inResultsView = sself.didAnswerQuestion || self.isOwnerOfQuestion;
if (sself.questionFullyLoaded) {
return;
} …
}
}
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13. ReactiveCocoa to the Rescue!
•
Signals instead of mutable variables
•
RACSignal – Think of it as a beacon sending out new values to it’s
subscribers

14. RACSignal
•
A unified interface for observing and reacting to all kinds of events
and their values
•
UI Action
•
Async Network Call
•
KVO
•
Async Processing
t’s
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ll
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pu

15. RACSignal
•
Shared vocabulary for transforming the received values
•
•
Combine, filter, reduce, map, and many more operations
Eventually generate output (side effects)
•
Updating a label
•
Update an array with objects from the network
•
etc.

16. - (void)viewDidLoad {
[super viewDidLoad];
[self.username
addTarget:self
action:@selector(textFieldTextDidChange:)
forControlEvents:UIControlEventAllEditingEvents];
[self.email
addTarget:self
action:@selector(textFieldTextDidChange:)
forControlEvents:UIControlEventAllEditingEvents];
Your name
Your email address
Sign Up
abled
ton.en
ut
gnUpB
si
}
!
- (void)textFieldTextDidChange:(UITextField *)field {
BOOL validUsername = self.username.text.length > 0;
NSRange at = [self.email.text rangeOfString:@"@"];
BOOL validEmail = at.location != NSNotFound;
self.signupButton.enabled = validUsername &&
validEmail;
}
Old
Solved the imperative way.

17. Your name
Your email address
RAC(self.signUpButton, enabled) = [RACSignal
combineLatest:@[
self.name.rac_textSignal,
self.email.rac_textSignal
]
reduce:^(NSString *name, NSString *email) {
NSRange at = [email rangeOfString:@"@"];
return @(at.location != NSNotFound && name.length > 0);
}];
Sign Up
ould I
Sh
SOME
AWE
bled?
e ena
b
Solved the reactive way.

18. Your name
Your email address
RAC(self.signUpButton, enabled) = [RACSignal
combineLatest:@[
self.name.rac_textSignal,
self.email.rac_textSignal
]
reduce:^(NSString *name, NSString *email) {
NSRange at = [email rangeOfString:@"@"];
return @(at.location != NSNotFound && name.length > 0);
}];
Sign Up
ould I
Sh
SOME
AWE
bled?
e ena
b
Solved the reactive way.

19. Network Validation?
Easy.
Your name
Your email address
Sign Up
RACSignal *validateEmailSignal = [self.email.rac_textSignal
map:^id(NSString *emailString) {
return [MyAPI validatedEmail:emailString];
}];
uld I
Sho
bled?
be ena
!
RAC(self.signUpButton, enabled) = [RACSignal
combineLatest:@[
self.name.rac_textSignal,
validateEmailSignal
]
reduce:^(NSString *name, APIResponse *response) {
return @(response.json.isValid == YES && name.length > 0);
}];
SOME
AWE
Solved the reactive way.

20. Network Validation?
Easy.
Your name
Your email address
Sign Up
RACSignal *validateEmailSignal =
map
}];
!
uld I
Sho
The point is to Minimize State
RAC
combineLatest
]
reduce
}];
Solved the
SOME
AWE
bled?
be ena

21. Network Validation?
Easy.
Your name
Your email address
Sign Up
RACSignal *validateEmailSignal =
map
}];
!
uld I
Sho
The point is to Minimize State
RAC
combineLatest
]
reduce
}];
Solved the
SOME
AWE
bled?
be ena

22. Check out ReactiveCocoa
Your Brain Will Thank You
https://github.com/ReactiveCocoa/ReactiveCocoa
Bob Spryn
LoHi Labs
@sprynmr (github, twitter)
!
Thanks to @jspahrsummers, @joshaber, @AshFurrow, @robb, @andrewsardone and @erikprice (github usernames)
for sharing their presentation slides and helping me learn ReactiveCocoa