ReactiveCocoa

Transcript

1. ReactiveCocoa OR: How I stopped worrying about state and love

   FRP

2.  ✉   robb robb@robb.is tmp ceterum_censeo

3. Let’s talk about State

4. evil √

5. Have you tried turning it off and on again?

6. Have you tried turning it off and on again? Have

   you tried turning it off and on again?

7. state

8. @property (readwrite, …) BOOL quacksLikeADuck; @property (readwrite, …) BOOL walksLikeADuck;

   @property (readonly, …) BOOL probablyADuck;

9. + (NSSet *)keyPathsForValuesAffectingProbablyADuck { return [NSSet setWithObjects:@”walksLikeADuck”, @”quacksLikeADuck”, nil]; }

   - (BOOL)isProbablyADuck { return _quacksLikeADuck && _walksLikeADuck; }

10. ReactiveCocoa

11. RAC(self.probablyADuck) = [RACSignal combineLatest:@[ RACAbleWithStart(self.walksLikeADuck), RACAbleWithStart(self.quacksLikeADuck) ] reduce:^(NSNumber *walks, NSNumber

    *quacks) { return @(walks.boolValue && quaks.boolValue); }];
12. None

13. [self.usernameField addTarget:self action:@selector(textFieldDidUpdate:) forControlEvents:UIControlEventEditingChanged]; [self.emailField addTarget:self action:@selector(textFieldDidUpdate:) forControlEvents:UIControlEventEditingChanged]; - (void)textFieldDidUpdate:(UITextField

    *)textField { BOOL validUsername = self.usernameField.text.length > 0; BOOL validEmail = [self.emailField.text uik_isEmail]; self.signupButton.enabled = validEmail && validUsername; }

14. because programming

15. [self.usernameField addTarget:self action:@selector(textFieldDidUpdate:) forControlEvents:UIControlEventEditingChanged]; [self.emailField addTarget:self action:@selector(textFieldDidUpdate:) forControlEvents:UIControlEventEditingChanged]; - (void)textFieldDidUpdate:(UITextField

    *)textField { BOOL validUsername = self.usernameField.text.length > 0; BOOL validEmail = [self.emailField.text uik_isEmail]; self.signupButton.enabled = validEmail && validUsername; }

16. RAC(self.signupButton.enabled) = [RACSignal combineLatest:@[ self.usernameField.rac_textSignal, self.emailField.rac_textSignal ] reduce:^(NSString *username, NSString

    *email) { BOOL validUsername = username.length > 0; BOOL validEmail = [email uik_isEmail]; return @(validUsername && validEmail); }];

17. FRP

18. None
19. None

20. ReactiveCocoa

21. @YES @NO @YES RACSignal

22. <UIControlEventEditingChanged> RACSignal

23. {“json_string”: “ohai”} RACSignal

24. RACSignal - (void)sendNext:(id)value; - (void)sendCompleted; - (void)sendError:(NSError *)error;

25. so, what?

26. map, reduce, filter

27. Let’s talk about Asynchrony

28. None

29. Blocks are awesome

30. void (^cb)(id operation, id result); void (^cb)(id operation, NSError *error);

    void (^cb)(id result, NSError *error); void (^cb)(NSError *error, id result);

31. [client logIn:^{ [client loadMeUser:^(UIKUser *user) { [client loadNewslettersForUser:user success:^(NSArray *result)

    NSLog(@"Your newsletters: %@", array); } failure:^(NSError *error) { // … }]; } failure:^(NSError *error) { // … }]; } failure:^(NSError *error) { // … }];

32. RACSignal

33. - (RACSignal *)logIn; - (RACSignal *)loadMeUser; - (RACSignal *)loadNewslettersForUser:(…)user;

34. [[[[client logIn] sequenceNext:^{ return [client loadMeUser]; }] flattenMap:^(UIKUser *user) {

    return [client loadNewslettersForUser:user]; }] subscribeNext:^(NSArray *newsletters) { NSLog(@"Your newsletters: %@", newsletters); } error:^(NSError *error) { // … }];
35. None

36. - (RACSignal *)validateEmail:(NSString *)email;

37. RACSignal *validEmail = [[self.emailField.rac_textSignal map:^(NSString *email) { return [[client validateEmail:email]

    startWith:@NO]; }] switchToLatest]; RACSignal *validForm = [RACSignal combineLatest:@[ validUsername, validEmail ] reduce:^(NSNumber *a, NSNumber *b) { return @(a.boolValue && b.boolValue); }]; RAC(self.signupButton.enabled) = validForm;
38. None

39. where's the catch?

40. •conceptual overhead •debugging can get tricky (logAll is your friend)

    •forces you to think

41. should I use it?

42. Probably!

43. state

44. None