Introduction to Coordinator's approach for resolving navigation in iOS applications. Presented on internal tech talks at Freeletics 27.02.2018.

1. Coordinate your app
Aydar Mukhametzyanov

2. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo
Agenda

3. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo

4. Intro to iOS navigation
UIViewController
UINavigationController
UIViewController
UIViewController
UIViewController
UIViewController
Navigation stack

5. UINavigationController
Intro to iOS navigation
UIViewControllerUIViewController
Push - Pop

6. UINavigationController
Intro to iOS navigation
UIViewController
Present - Dismiss
UINavigationController
UIViewController

7. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo

8. Problems
1. Push next
2. Go back

9. E
new
D E
newnew
D
C
Problems
A B C
visible
Push next
A B
visible
+1
+n

10. D EC
ED
Problems
A B C
visible
Go back
A B
visible
-1
-n

11. Problems
1. Push next
2. Go back
+1 +n
-1 -n

12. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo

13. Classic solution
Chained navigation

14. Classic solution
Chained navigation
EDA B C
let vc = E()
push(vc)
+1

15. Classic solution
Chained navigation
EA B C D

16. Classic solution
Chained navigation
EA B C D
PM N O D

17. D
Classic solution
...
func showNext() {
let vc: UIViewController
if isOneFlow {
vc = E()
} else {
vc = P()
}
push(vc)
}
...
Chained navigation

18. Classic solution
Chained navigation
D
E
P
…
+ Conditions

19. Classic solution
Chained navigation
EDA B C
pop()
-1

20. Classic solution
Chained navigation
EDA B C
pop(to: c)
-n

21. Classic solution
Chained navigation
E
C
…
+ How it was presented

22. Classic solution
Chained navigation
Screen object
knows and does too much

23. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo

24. Solution with Coordinators
EDA B C

25. Solution with Coordinators
EDA B C

26. Solution with Coordinators
EDA B C
Coordinator
1. done
2. init
push
3. done
4. init
push

27. Solution with Coordinators
EDA B C
Coordinator
1. done
2. init
push
3. done
4. init
push

28. Solution with Coordinators
BCoordinator
private let onDone: () -> ()
...
func donePressed() {
onDone()
}
...
private func configuredA() -> A {
let a = A(onDone: {
self.navigationController?
.push(configuredB())
})
return a
}
private func configuredB() -> B {
let b = B(onDone: {
self.navigationController?
.push(configuredC())
})
return b
}
…

29. Solution with Coordinators
EDA B C
Coordinator

30. Solution with Coordinators
EDA B C
Coordinator
IF G H
😱

31. Solution with Coordinators
EDA B C
Coordinator
IF G H
Coordinator
2

32. Solution with Coordinators
Coordinator
Child
coordinator
private func startChildCoordinator() {
let coord = ChildCoordinator(onFinish: {
self.navigationController?.dismiss()
})
navigationController?.present(coord.start())
}
init(onFinish: @escaping () -> ()) {
self.onFinish = onFinish
}
...
private func configuredI() -> I {
let i = I(onDone: {
self.onFinish()
})
return i
}

33. Solution with Coordinators
EDA B C
Coordinator
Coordinator
2

34. 👍
Solution with Coordinators
A B
Coordinator
Coordinator
2
Coordinator
3

35. Solution with Coordinators
1. Push next
2. Go back
+1 +n
-1 -n

36. Solution with Coordinators
+1 +n
EDA B C
Coord A
onDone() push(e)
visible
-1

37. Solution with Coordinators
EDA B C
Coord A
+1 +n -1

38. Solution with Coordinators
EDA B C
Coord A
PM N O D
Coord B
+1 +n -1

39. Solution with Coordinators
1. Push next
2. Go back
+1 +n
-1 -n

40. Solution with Coordinators
A
Coordinator
EB C D
visible
-n

41. Solution with Coordinators
D E
Coordinator
2
A
Coordinator
B C
-n
visible
onDone()

42. Solution with Coordinators
Coordinator
private func startChildCoordinator() {
let topVC = navigationController!.topViewController
let coord = ChildCoordinator(onFinish: {
self.navigationController?.pop(to: topVC)
})
navigationController?.push(coord.start())
}
-n

43. Solution with Coordinators
1. Push next
2. Go back
+1 +n
-1 -n

44. Solution with Coordinators
+1
+n
-1
-n
Chained navigation Coordinators
OK, but dependencies
OK, but dependencies
OK
NOT OK
OK
OK
OK
OK

45. • Intro to iOS navigation
• Problems
• Classic solution
• Solution with Coordinators
• Demo

46. Demo
https://github.com/aydarin/mvvm-demo

47. Thank you! 🎉
Questions