Software architecture has a lot to do with making sure the dependency graph is well structured. But in practice, maintaining a clean dependency graph while injecting dependencies in a type safe and runtime safe manner is a lot of repetitive code to write. This problem often leads developers to overuse the singleton pattern, making their code less modular at best, almost untestable at worst. Weaver is a code generation tool which makes it easy to inject dependencies where they are needed while maintaining a safe and clean dependency graph at the same time. Talk: https://www.youtube.com/watch?v=h3CMMbgozG0 Github: https://github.com/scribd/Weaver

1. MAINTAINING A DEPENDENCY GRAPH WITHMAINTAINING A DEPENDENCY GRAPH WITH
WEAVERWEAVER

2. THÉOPHANE RUPINTHÉOPHANE RUPIN
@thrupin

3. DI ContainerDI Container

4. DI ContainerDI Container
An object able to instantiate, retain, and resolve other
objects’ dependencies.

5. Dependency GraphDependency Graph

6. final class Foo {
let bar: Bar
init(bar: Bar) {
self.bar = bar
bar.foo = self
}
func barDidSomething() { ... }
}
final class Bar {
weak var foo: Foo?
func doSomething() { foo?.barDidSomething() }
}

7. Weaver is a code generation tool which makes it easy
to inject dependencies.
https://github.com/scribd/Weaver

8. WHY?WHY?

9. WHY?WHY?
I could not nd any satisfying compile time DI solution,
so I gave it a try.

10. ADVANTAGESADVANTAGES

11. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.

12. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.

13. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.
3. Type safety. If it compiles, it works!

14. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.
3. Type safety. If it compiles, it works!
4. Declarativeness.

15. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.
3. Type safety. If it compiles, it works!
4. Declarativeness.
5. No optionality. If it's declared, it's there.

16. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.
3. Type safety. If it compiles, it works!
4. Declarativeness.
5. No optionality. If it's declared, it's there.
6. Thread safety. Immutability. No lazy loading.

17. ADVANTAGESADVANTAGES
1. Mimics manual DI technics. No black box.
2. Compile time errors. Fails fast.
3. Type safety. If it compiles, it works!
4. Declarativeness.
5. No optionality. If it's declared, it's there.
6. Thread safety. Immutability. No lazy loading.
7. No additional framework to ship.

18. DRAWBACKSDRAWBACKS

19. DRAWBACKSDRAWBACKS
1. More code to compile. Can be optimized.

20. DRAWBACKSDRAWBACKS
1. More code to compile. Can be optimized.
2. Meta-programmation is hard.

21. DRAWBACKSDRAWBACKS
1. More code to compile. Can be optimized.
2. Meta-programmation is hard.
3. Use of pseudo annotations.

22. DRAWBACKSDRAWBACKS
1. More code to compile. Can be optimized.
2. Meta-programmation is hard.
3. Use of pseudo annotations.
4. Experimental.

23. LET'S SEE IN PRACTICELET'S SEE IN PRACTICE

25. A logical dependency graph

26. HOW COULD WE PROVIDEHOW COULD WE PROVIDE URLSessionURLSession??

27. Sharing an instance of URLSession
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
}

28. Sharing an instance of URLSession
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
static var shared: AppDelegate? {
return UIApplication.shared.delegate as? AppDelegate
}
}

29. Sharing an instance of URLSession
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
static var shared: AppDelegate? {
return UIApplication.shared.delegate as? AppDelegate
}
let urlSession: URLSession = {
let config = ...
return URLSession(configuration: config)
}()
}

30. Using the shared instance of URLSession
final class APIClient {
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

31. Using the shared instance of URLSession
final class APIClient {
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
AppDelegate.shared.urlSession.dataTask(with: url) {
...
}.resume()
}
}

33. Not so good...

34. Injecting a shared instance of URLSession in
APIClient
final class APIClient {
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

35. Injecting a shared instance of URLSession in
APIClient
final class APIClient {
private let urlSession: URLSession
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

36. Injecting a shared instance of URLSession in
APIClient
final class APIClient {
private let urlSession: URLSession
init(urlSession: URLSession = AppDelegate.shared.urlSession)
self.urlSession = urlSession
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

37. Injecting a shared instance of URLSession in
APIClient
final class APIClient {
private let urlSession: URLSession
init(urlSession: URLSession = AppDelegate.shared.urlSession)
self.urlSession = urlSession
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
urlSession.dataTask(with: url) { ... }.resume()
}
}

38. Using APIClient in MovieManager
final class MovieManager {
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

39. Using APIClient in MovieManager
final class MovieManager {
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
APIClient().get("http://my_movie_api/movies") { ... }
}
}

40. Using APIClient in MovieManager
final class MovieManager {
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
APIClient().get("http://my_movie_api/movies") { ... }
// ^ No URLSession to pass in.
}
}

42. Try again...

43. Passing down an instance of URLSession in
APIClient
final class APIClient {
private let urlSession: URLSession
init(_ urlSession: URLSession) {
self.urlSession = urlSession
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
urlSession.dataTask(with: url) { ... }.resume()
}
}

44. Passing down an instance of URLSession in
APIClient
final class APIClient {
private let urlSession: URLSession
init(_ urlSession: URLSession) { // <- No default anymore
self.urlSession = urlSession
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
urlSession.dataTask(with: url) { ... }.resume()
}
}

45. From MovieManager to APIClient
final class MovieManager {
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

46. From MovieManager to APIClient
final class MovieManager {
private let apiClient: APIClient
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

47. From MovieManager to APIClient
final class MovieManager {
private let apiClient: APIClient
init(urlSession: URLSession) {
apiClient = APIClient(urlSession)
}
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

48. From MovieManager to APIClient
final class MovieManager {
private let apiClient: APIClient
init(urlSession: URLSession) {
apiClient = APIClient(urlSession)
}
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
apiClient.get("http://my_movie_api/movies") { ... }
}
}

49. From HomeViewController to MovieManager
final class HomeViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
}

50. From HomeViewController to MovieManager
final class HomeViewController {
private let movieManager: MovieManager
override func viewDidLoad() {
super.viewDidLoad()
}
}

51. From HomeViewController to MovieManager
final class HomeViewController {
private let movieManager: MovieManager
init(_ urlSession: URLSession) {
movieManager = MovieManager(urlSession: urlSession)
}
override func viewDidLoad() {
super.viewDidLoad()
}
}

52. From HomeViewController to MovieManager
final class HomeViewController {
private let movieManager: MovieManager
init(_ urlSession: URLSession) {
movieManager = MovieManager(urlSession: urlSession)
}
override func viewDidLoad() {
super.viewDidLoad()
movieManager.getMovies { ... }
}
}

53. From AppDelegate to HomeViewController
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
}
}

54. From AppDelegate to HomeViewController
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let configuration = ...
let urlSession = URLSession(configuration: configuration)
}
}

55. From AppDelegate to HomeViewController
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let configuration = ...
let urlSession = URLSession(configuration: configuration)
let controller = HomeViewController(urlSession)
...
}
}

57. Well done!

58. WHY IS THIS BETTER?WHY IS THIS BETTER?

59. WHY IS THIS BETTER?WHY IS THIS BETTER?
MODULARITYMODULARITY

60. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
}

61. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
init() {
}
}

62. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
init() {
let configuration = ...
}
}

63. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
init() {
let configuration = ...
config.urlCache?.diskCapacity = 1024 * 1024 * 50
config.urlCache?.memoryCapacity = 1024 * 1024 * 5
}
}

64. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
init() {
let configuration = ...
config.urlCache?.diskCapacity = 1024 * 1024 * 50
config.urlCache?.memoryCapacity = 1024 * 1024 * 5
let urlSession = URLSession(configuration: configuration)
}
}

65. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
private let apiClient: APIClient
init() {
let configuration = ...
config.urlCache?.diskCapacity = 1024 * 1024 * 50
config.urlCache?.memoryCapacity = 1024 * 1024 * 5
let urlSession = URLSession(configuration: configuration)
apiClient = APIClient(urlSession)
}
}

66. What if ImageManager needs a bigger HTTP cache?
final class ImageManager {
private let apiClient: APIClient
init() {
let configuration = ...
config.urlCache?.diskCapacity = 1024 * 1024 * 50
config.urlCache?.memoryCapacity = 1024 * 1024 * 5
let urlSession = URLSession(configuration: configuration)
apiClient = APIClient(urlSession)
}
func getImage(_ image: String, completion: @escaping (UIImage
apiClient.get("http://my_movie_api/images/(image)") { ..
}
}

68. That was easy!

69. Great! But this is too much code to write...

70. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
)
}
}

71. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
)
}
}

72. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
analyticsManager: analyticsManager,
)
}
}

73. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
analyticsManager: analyticsManager,
reachabilityManager: reachabilityManager,
)
}
}

74. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
analyticsManager: analyticsManager,
reachabilityManager: reachabilityManager,
logger: logger,
)
}
}

75. In a real project, we'd have to pass down dozens of
dependencies
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
analyticsManager: analyticsManager,
reachabilityManager: reachabilityManager,
logger: logger,
...
)
}
}

76. In a real project, we'd have to pass down dozens of
dependencies
Ouch!
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
func applicationDidFinishLaunching(_ application: UIApplicati
let controller = HomeViewController(
sessionManager: sessionManager,
analyticsManager: analyticsManager,
reachabilityManager: reachabilityManager,
logger: logger,
...
)
}
}

77. THAT'S WHERE WEAVER COMES HANDY.THAT'S WHERE WEAVER COMES HANDY.

78. WHAT METHODOLOGY HAVE WE USED SO FAR?WHAT METHODOLOGY HAVE WE USED SO FAR?

79. WHAT METHODOLOGY HAVE WE USED SO FAR?WHAT METHODOLOGY HAVE WE USED SO FAR?
1. Looked at the code.

80. WHAT METHODOLOGY HAVE WE USED SO FAR?WHAT METHODOLOGY HAVE WE USED SO FAR?
1. Looked at the code.
2. Built a representation of the dependency graph.

81. WHAT METHODOLOGY HAVE WE USED SO FAR?WHAT METHODOLOGY HAVE WE USED SO FAR?
1. Looked at the code.
2. Built a representation of the dependency graph.
3. Made sure the dependency graph was ok.

82. WHAT METHODOLOGY HAVE WE USED SO FAR?WHAT METHODOLOGY HAVE WE USED SO FAR?
1. Looked at the code.
2. Built a representation of the dependency graph.
3. Made sure the dependency graph was ok.
4. Used a DI technique to implement the graph.

83. WEAVER DOES THE SAMEWEAVER DOES THE SAME

84. WEAVER DOES THE SAMEWEAVER DOES THE SAME BUT AUTOMATICALLYBUT AUTOMATICALLY

85. WEAVER DOES THE SAMEWEAVER DOES THE SAME BUT AUTOMATICALLYBUT AUTOMATICALLY
1. Scans the code, looking for annotations.

86. WEAVER DOES THE SAMEWEAVER DOES THE SAME BUT AUTOMATICALLYBUT AUTOMATICALLY
1. Scans the code, looking for annotations.
2. Builds a representation of the dependency graph.

87. WEAVER DOES THE SAMEWEAVER DOES THE SAME BUT AUTOMATICALLYBUT AUTOMATICALLY
1. Scans the code, looking for annotations.
2. Builds a representation of the dependency graph.
3. Validates the dependency graph.

88. WEAVER DOES THE SAMEWEAVER DOES THE SAME BUT AUTOMATICALLYBUT AUTOMATICALLY
1. Scans the code, looking for annotations.
2. Builds a representation of the dependency graph.
3. Validates the dependency graph.
4. Generates the code to implement the graph.

89. BACK TO OUR EXAMPLEBACK TO OUR EXAMPLE

90. Referencing to URLSession in APIClient

91. Referencing to URLSession in APIClient
final class APIClient {
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

92. Referencing to URLSession in APIClient
final class APIClient {
private let dependencies: APIClientDependencyResolver
init(injecting dependencies: APIClientDependencyResolver) {
self.dependencies = dependencies
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

93. Referencing to URLSession in APIClient
final class APIClient {
private let dependencies: APIClientDependencyResolver
// weaver: urlSession <- URLSession
init(injecting dependencies: APIClientDependencyResolver) {
self.dependencies = dependencies
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
}
}

94. Referencing to URLSession in APIClient
final class APIClient {
private let dependencies: APIClientDependencyResolver
// weaver: urlSession <- URLSession
init(injecting dependencies: APIClientDependencyResolver) {
self.dependencies = dependencies
}
func get(_ url: URL, completion: @escaping (Data?) -> Void) ->
dependencies.urlSession.dataTask(with: url) { ... }.resum
}
}

95. Referencing to URLSession in APIClient
GENERATED CODEGENERATED CODE

96. Referencing to URLSession in APIClient
GENERATED CODEGENERATED CODE
protocol APIClientInputDependencyResolver {
var urlSession: URLSession { get }
}

97. Referencing to URLSession in APIClient
GENERATED CODEGENERATED CODE
protocol APIClientInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol APIClientDependencyResolver {
var urlSession: URLSession { get }
}

98. Referencing to URLSession in APIClient
GENERATED CODEGENERATED CODE
protocol APIClientInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol APIClientDependencyResolver {
var urlSession: URLSession { get }
}
final class APIClientDependencyContainer: APIClientDependencyReso
let urlSession: URLSession
init(injecting dependencies: APIClientInputDependencyResolver
urlSession = dependencies.urlSession
}
}

99. Registering APIClient in MovieManager
final class MovieManager {
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

100. Registering APIClient in MovieManager
final class MovieManager {
private let dependencies: MovieManagerDependencyResolver
init(injecting dependencies: MovieManagerDependencyResolver)
self.dependencies = dependencies
}
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

101. Registering APIClient in MovieManager
final class MovieManager {
private let dependencies: MovieManagerDependencyResolver
// weaver: apiClient = APIClient
init(injecting dependencies: MovieManagerDependencyResolver)
self.dependencies = dependencies
}
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
}
}

102. Registering APIClient in MovieManager
final class MovieManager {
private let dependencies: MovieManagerDependencyResolver
// weaver: apiClient = APIClient
init(injecting dependencies: MovieManagerDependencyResolver)
self.dependencies = dependencies
}
func getMovies(_ completion: @escaping ([Movie]?) -> Void) {
dependencies.apiClient.get("http://my_movie_api/movies")
}
}

103. Registering APIClient in MovieManager
GENERATED CODEGENERATED CODE

104. Registering APIClient in MovieManager
GENERATED CODEGENERATED CODE
protocol MovieManagerInputDependencyResolver {
var urlSession: URLSession { get }
}

105. Registering APIClient in MovieManager
GENERATED CODEGENERATED CODE
protocol MovieManagerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol MovieManagerDependencyResolver {
var apiClient: APIClient { get }
}

106. Registering APIClient in MovieManager
GENERATED CODEGENERATED CODE
protocol MovieManagerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol MovieManagerDependencyResolver {
var apiClient: APIClient { get }
}
final class MovieManagerDependencyContainer: MovieManagerDependencyResolv
let urlSession: URLSession
var apiClient: APIClient {
let dependencies = APIClientDependencyContainer(injecting: self)
return APIClient(injecting: dependencies)
}
init(injecting dependencies: MovieManagerInputDependencyResolver) {
urlSession = dependencies.urlSession
}
}

107. Registering APIClient in MovieManager
GENERATED CODEGENERATED CODE
protocol MovieManagerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol MovieManagerDependencyResolver {
var apiClient: APIClient { get }
}
final class MovieManagerDependencyContainer: MovieManagerDependencyResolv
let urlSession: URLSession
var apiClient: APIClient {
let dependencies = APIClientDependencyContainer(injecting: self)
return APIClient(injecting: dependencies)
}
init(injecting dependencies: MovieManagerInputDependencyResolver) {
urlSession = dependencies.urlSession
}
}
extension MovieManagerDependencyContainer: APIClientInputDependencyResolv

108. Registering MovieManager in
HomeViewController
final class HomeViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
}

109. Registering MovieManager in
HomeViewController
final class HomeViewController {
private let dependencies: HomeViewControllerDependencyResolve
init(injecting dependencies: HomeViewControllerDependencyReso
self.dependencies = dependencies
}
override func viewDidLoad() {
super.viewDidLoad()
}
}

110. Registering MovieManager in
HomeViewController
final class HomeViewController {
private let dependencies: HomeViewControllerDependencyResolve
// weaver: movieManager = MovieManager
init(injecting dependencies: HomeViewControllerDependencyReso
self.dependencies = dependencies
}
override func viewDidLoad() {
super.viewDidLoad()
}
}

111. Registering MovieManager in
HomeViewController
final class HomeViewController {
private let dependencies: HomeViewControllerDependencyResolve
// weaver: movieManager = MovieManager
init(injecting dependencies: HomeViewControllerDependencyReso
self.dependencies = dependencies
}
override func viewDidLoad() {
super.viewDidLoad()
dependencies.movieManager.getMovies { ... }
}
}

112. Registering MovieManager in
HomeViewController
GENERATED CODEGENERATED CODE

113. Registering MovieManager in
HomeViewController
GENERATED CODEGENERATED CODE
protocol HomeViewControllerInputDependencyResolver {
var urlSession: URLSession { get }
}

114. Registering MovieManager in
HomeViewController
GENERATED CODEGENERATED CODE
protocol HomeViewControllerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol HomeViewControllerDependencyResolver {
var movieManager: MovieManager { get }
}

115. Registering MovieManager in
HomeViewController
GENERATED CODEGENERATED CODE
protocol HomeViewControllerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol HomeViewControllerDependencyResolver {
var movieManager: MovieManager { get }
}
final class HomeViewControllerDependencyContainer: HomeViewControllerDepe
let urlSession: URLSession
var movieManager: MovieManager {
let dependencies = MovieManagerDependencyContainer(injecting: sel
return MovieManager(injecting: dependencies)
}
init(injecting dependencies: HomeViewControllerInputDependencyResolve
urlSession = dependencies.urlSession
}
}

116. Registering MovieManager in
HomeViewController
GENERATED CODEGENERATED CODE
protocol HomeViewControllerInputDependencyResolver {
var urlSession: URLSession { get }
}
protocol HomeViewControllerDependencyResolver {
var movieManager: MovieManager { get }
}
final class HomeViewControllerDependencyContainer: HomeViewControllerDepe
let urlSession: URLSession
var movieManager: MovieManager {
let dependencies = MovieManagerDependencyContainer(injecting: sel
return MovieManager(injecting: dependencies)
}
init(injecting dependencies: HomeViewControllerInputDependencyResolve
urlSession = dependencies.urlSession
}
}
extension HomeViewControllerDependencyContainer: MovieManagerInputDepende

117. COMPILING...COMPILING...

118. COMPILING...COMPILING...
Oops!
URLSession cannot be resolved

120. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
}

121. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
}

122. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
// weaver: urlSession = URLSession
}

123. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
}

124. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
// weaver: urlSession.builder = AppDelegate.makeURLSession
}

125. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
// weaver: urlSession.builder = AppDelegate.makeURLSession
static func makeURLSession(_: AppDelegateDependencyResolver)
let configuration = ...
return URLSession(configuration: configuration)
}
}

126. Registering URLSession in AppDelegate
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
private let dependencies = AppDelegateDependencyContainer()
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
// weaver: urlSession.builder = AppDelegate.makeURLSession
static func makeURLSession(_: AppDelegateDependencyResolver)
let configuration = ...
return URLSession(configuration: configuration)
}
// weaver: homeViewController = HomeViewController
}

127. Registering URLSession in AppDelegate
GENERATED CODEGENERATED CODE

128. Registering URLSession in AppDelegate
GENERATED CODEGENERATED CODE
protocol AppDelegateDependencyResolver {
var homeViewController: HomeViewController { get }
}

129. Registering URLSession in AppDelegate
GENERATED CODEGENERATED CODE
protocol AppDelegateDependencyResolver {
var homeViewController: HomeViewController { get }
}
final class AppDelegateDependencyContainer: AppDelegateDependencyResolver
let urlSession: URLSession
var homeViewController: HomeViewController {
let dependencies = HomeViewControllerDependencyContainer(injectin
return HomeViewController(injecting: dependencies)
}
init() {
urlSession = URLSession.makeURLSession(self)
}
}

130. Registering URLSession in AppDelegate
GENERATED CODEGENERATED CODE
protocol AppDelegateDependencyResolver {
var homeViewController: HomeViewController { get }
}
final class AppDelegateDependencyContainer: AppDelegateDependencyResolver
let urlSession: URLSession
var homeViewController: HomeViewController {
let dependencies = HomeViewControllerDependencyContainer(injectin
return HomeViewController(injecting: dependencies)
}
init() {
urlSession = URLSession.makeURLSession(self)
}
}
extension AppDelegateDependencyContainer: HomeViewControllerInputDependen

132. It works!

133. STILL MODULAR?STILL MODULAR?

134. STILL MODULAR?STILL MODULAR?
YESYES

135. Registering URLSession with a bigger HTTP cache in
ImageManager
final class ImageManager {
}

136. Registering URLSession with a bigger HTTP cache in
ImageManager
final class ImageManager {
private let dependencies: ImageManagerDependencyResolver
init(injecting dependencies: ImageManagerDependencyResolver) { self.d
}

137. Registering URLSession with a bigger HTTP cache in
ImageManager
final class ImageManager {
private let dependencies: ImageManagerDependencyResolver
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
// weaver: urlSession.builder = ImageManager.makeURLSession
init(injecting dependencies: ImageManagerDependencyResolver) { self.d
}

138. Registering URLSession with a bigger HTTP cache in
ImageManager
final class ImageManager {
private let dependencies: ImageManagerDependencyResolver
// weaver: urlSession = URLSession
// weaver: urlSession.scope = .container
// weaver: urlSession.builder = ImageManager.makeURLSession
init(injecting dependencies: ImageManagerDependencyResolver) { self.d
static func makeURLSession(_: ImageManagerDependencyResolver) -> URLS
let configuration = ...
configuration.urlCache?.diskCapacity = 1024 * 1024 * 50
configuration.urlCache?.memoryCapacity = 1024 * 1024 * 5
return URLSession(configuration: configuration)
}
}

139. Registering URLSession in ImageManager
GENERATED CODEGENERATED CODE

140. Registering URLSession in ImageManager
GENERATED CODEGENERATED CODE
protocol ImageManagerDependencyResolver {
var apiClient: APIClient { get }
}

141. Registering URLSession in ImageManager
GENERATED CODEGENERATED CODE
protocol ImageManagerDependencyResolver {
var apiClient: APIClient { get }
}
final class ImageManagerDependencyContainer: ImageManagerDependencyResolv
let urlSession: URLSession
var apiClient: APIClient {
let dependencies = APIClientDependencyContainer(injecting: self)
return APIClient(injecting: dependencies)
}
init() {
urlSession = URLSession.makeURLSession(self)
}
}

142. Registering URLSession in ImageManager
GENERATED CODEGENERATED CODE
protocol ImageManagerDependencyResolver {
var apiClient: APIClient { get }
}
final class ImageManagerDependencyContainer: ImageManagerDependencyResolv
let urlSession: URLSession
var apiClient: APIClient {
let dependencies = APIClientDependencyContainer(injecting: self)
return APIClient(injecting: dependencies)
}
init() {
urlSession = URLSession.makeURLSession(self)
}
}
extension ImageManagerDependencyContainer: APIClientInputDependencyResolv

144. Works out of the box

145. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT

146. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.

147. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.
Dependency graph visualizer.

148. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.
Dependency graph visualizer.
Dependency graph optimizations.

149. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.
Dependency graph visualizer.
Dependency graph optimizations.
Detect retain cycles.

150. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.
Dependency graph visualizer.
Dependency graph optimizations.
Detect retain cycles.
Detect suspicious graph shapes.

151. ROOM FOR IMPROVEMENTROOM FOR IMPROVEMENT
Adopt Weaver more widely at Scribd.
Dependency graph visualizer.
Dependency graph optimizations.
Detect retain cycles.
Detect suspicious graph shapes.
...

152. THE END.THE END.