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

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

?

Program Smarter

Not just another API.

It enables you to

Focus on WHAT not HOW

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

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

• Setup your reactions

• Compose, split, filter, etc.

ImperativeThe way we normally program.

ImperativeThe 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

Auto-layout : Managing Frames ReactiveCocoa : Imperative programming

Complexity Is

STATE

BOOL loadingNextPageOfComments;

BOOL commentsAreShowing;

BOOL commentsLoadingShowing;

BOOL flippingAnswers;

BOOL isOwnerOfQuestion;

2 states

4 states

8 states

16 states

32 states

- (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; self.commentsLoadingShowing = YES; … } [self showCommentBox:self.inResultsView || self.isOwnerOfQuestion]; } !^aBlock { sself.didAnswerQuestion = sself.question.userResponse ? YES : NO; sself.inResultsView = sself.didAnswerQuestion || self.isOwnerOfQuestion;

if (sself.questionFullyLoaded) { return; } …

}

Real code from one file

- (void) prepareForReuse { self.state = TCQuestionDetailViewControllerStateInactive; self.questionFullyLoaded = NO; self.isOwnerOfQuestion = NO; self.didAnswerQuestion = NO; [self showCommentBox:NO]; self.loadingNextPageOfComments = NO; self.commentsAreShowing = NO; self.commentsLoadingShowing = NO; }

ReactiveCocoa to the Rescue!

• Signals instead of mutable variables

• RACSignal – Think of it as a beacon sending out new values to it’s subscribers

RACSignal

• A unified interface for observing and reacting to all kinds of events and their values• UI Action• Async Network Call• KVO• Async Processing

It’s all input!

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.

- (void)viewDidLoad { [super viewDidLoad];

[self.username addTarget:self action:@selector(textFieldTextDidChange:) forControlEvents:UIControlEventAllEditingEvents];

[self.email addTarget:self action:@selector(textFieldTextDidChange:) forControlEvents:UIControlEventAllEditingEvents];} !- (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;}

Your name

Your email address

Sign Up

Solved the imperative way.

signUpButton.enabled

Old

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); }];

Your name

Your email address

Sign Up

Solved the reactive way.

Should I be enabled?

AWESOME

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); }];

Your name

Your email address

Sign Up

Solved the reactive way.

Should I be enabled?

AWESOME

RACSignal *validateEmailSignal = [self.email.rac_textSignal map:^id(NSString *emailString) { return [MyAPI validatedEmail:emailString]; }]; !RAC(self.signUpButton, enabled) = [RACSignal combineLatest:@[ self.name.rac_textSignal, validateEmailSignal ] reduce:^(NSString *name, APIResponse *response) { return @(response.json.isValid == YES && name.length > 0); }];

Solved the reactive way.AWESOME

Your name

Your email address

Sign Up

Should I be enabled?

Network Validation? Easy.

RACSignal *validateEmailSignal = map }];!RAC combineLatest ] reduce }];

Solved the AWESOME

Your name

Your email address

Sign Up

Should I be enabled?

Network Validation? Easy.

The point is to Minimize State

RACSignal *validateEmailSignal = map }];!RAC combineLatest ] reduce }];

Solved the AWESOME

Your name

Your email address

Sign Up

Should I be enabled?

Network Validation? Easy.

The point is to Minimize State

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