λ is coming to Obj-C – ReactiveCocoa

Transcript

1. λ is coming to Obj-C: ReactiveCocoa Vladimir @chippcheg Burdukov
2. Imperative
3. Declarative
4. Functional programming λ-calculus
5. Functional programming
6. Pure function • result doesn’t depend on any state • function doesn’t change any external state.
7. Pure function def sqr(x: Int): Int = x * x //> sqr: (x: Int)Int sqr(2) /> res4: Int = 4 def add1(x: Int): Int = x + 1 //> add1: (x: Int)Int add1(4) //> res3: Int = 5 add1(add1(4)) //> res4: Int = 6
8. Higher-order functions
9. Higher-order functions def sqr(x: Int): Int = x * x def sumF(x: Int, y: Int, f: Int => Int) = f(x) + f(y) sumF(3, 4, sqr) //> res5: Int = 25
10. Higher-order functions def sqr(x: Int): Int = x * x def sumF(x: Int, y: Int, f: Int => Int) = f(x) + f(y) sumF(3, 4, sqr) //> res5: Int = 25 sumF(-9, 16, abs) //> res6: Int = 25
11. Tail recursion
12. Tail recursion Lists Head Tail
13. Tail recursion Lists val foo: List[Int] = 1 to 5 toList //> foo : List[Int] = List(1, 2, 3, 4, 5) val foohead = foo.head //> foohead : Int = 1 val footail = foo.tail //> footail : List[Int] = List(2, 3, 4, 5)
14. Tail recursion def sumList(xs: List[Int]): Int = if (xs == Nil) return 0 else return xs.head + sumList(xs.tail) // > sumList: (xs: List[Int])Int ! sumList(foo) //> res3: Int = 15
15. Composition
16. Composition def f(a: String): String = "f(" + a + ")" f("5") //> res11: String = f(5) def g(a: String): String = "g(" + a + “)" g("5") //> res12: String = g(5) f(g("5")) //> res13: String = f(g(5)) def fg = f _ compose g _ //> fg: => String => String fg("5") //> res14: String = f(g(5))
17. Functional programming References •https://www.coursera.org/course/progfun
18. Reactive Programming
19. Reactive Programming 5 10 =SUM(A1;B1) A1 B1 C1
20. Functional Reactive Programming
21. ReactiveCocoa Next step of Objective-C evolution https://github.com/ReactiveCocoa/ReactiveCocoa/
22. Introduction https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/Documentation/
23. Introduction https://github.com/ReactiveCocoa/ReactiveCocoa/blob/master/Documentation/ pod
24. RACSequense RACSignal
25. RACSignal
26. RACSignal UISwitch *settingSwitch = [[UISwitch alloc] init]; RACSignal *switchSignal = [settingSwitch rac_signalForControlEvents:UIControlEventValueChanged]; [switchSignal subscribeNext:^(UISwitch *x) { NSLog(@"SWITCH %@", x.on); }]; //SWITCH 0 //SWITCH 1 //SWITCH 0
27. RACSignal signal subscribeNext:
28. RACSignal Composition [[[self.field rac_textSignal] filter:^BOOL(NSString *value) { return value.length >= 8; }] subscribeNext:^(id x) { NSLog(@"%@", x); }];
29. RACSignal Combining signal signal combine reduce YES/NO NSString NSString
30. RACSignal Combining RAC(self.createButton, enabled) = [RACSignal combineLatest:@[self.loginField.rac_textSignal, self.passwordField.rac_textSignal] reduce:^id(NSString *username, NSString *password) { return @(username.length > 0 && password.length > 0); }];
31. RACSequence
32. Binding RAC(self.avatarImageView, image) = RACObserve(self.viewModel, userAvatar);
33. ReactiveCocoa UI extensions • UIActionSheet / UIAlertView • UIButton • UITableViewCell • UIControl (rac_signalForControlEvents:) • UIGestureRecognizer • UITextField
34. UIAlertView Signal UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Something goes wrong" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:@"Retry", nil]; ! [[alertView rac_buttonClickedSignal] subscribeNext:^(NSNumber *buttonNumber) { NSLog(@"alert button: %@", [alertView buttonTitleAtIndex:buttonNumber.intValue]); }];
35. UIButton Command RACCommand *loginCommand = [[RACCommand alloc] initWithEnabled:[RACSignal combineLatest:@[loginField.rac_textSignal, passwordField.rac_textSignal] reduce:^id(NSString *username, NSString *password) { return @(username.length > 0 && password.length > 0); }] signalBlock:^RACSignal *(id input) { return [[JMHSync shared] loginUser:self.loginField.text withPassword:self.passwordField.text]; }]; ! self.createButton.rac_command = loginCommand;
36. UITextField Signal [self.loginField.rac_textSignal subscribeNext:^(NSString *x) { NSLog(@"you entered %@", x); }];
37. Conclusion
38. Questions
39. Thank you!