Injektion
Introduction
A simple way to handle dependency injection using property wrappers. It is available as a Swift Package or as a CocoaPod. The concept is heavily based on the work of Antoine van der Lee:
https://www.avanderlee.com/swift/dependency-injection/
Install
Swift Package
Injektion can be added to an Xcode project as a swift package. Using the regular Xcode tool, search for the following URL:
https://github.com/andrewmcgee/Injektion
Cocoapods
Injektion can be added to a project as a pod by adding the folloing to your Podfile under the correct target:
pod 'Injektion', '~> 1.0.0'
and then running the following command in yout terminal:
pod install
Usage
To set up a dependency, define a new (optionally private) key struct that conforms to the DependencyKey protocol. Its current value should be the dependency, which can be abstracted behind a protocol.
private struct SomeDependencyKey: DependencyKey {
static var currentValue: DependencyType = Dependency()
}
Then extend the Dependencies type to include a new key provider computed property. Its type should be the same as the DependencyKey‘s currentValue. Using its getter and setter it should act as a proxy for the static subscript of Dependencies that takes the implementation of DependencyKey‘s type defined above as an input.
extension Dependencies {
var dependencyKeyProvider: DependencyType {
get { Self[SomeDependencyKey.self] }
set { Self[SomeDependencyKey.self] = newValue }
}
}
With these parts in place, you can now refer to the dependency throughout you code in the following way:
class SomeClass {
@Dependency(\.dependencyKeyProvider) private var dependency: DependencyType
}
You can update a dependency in two ways. Either like this:
class SomeClass {
@Dependency(\.dependencyKeyProvider) private var dependency: DependencyType
func updateDependency() {
self.dependency = NewDependency()
}
}
or directly like this:
Dependencies[SomeDependencyKey.self] = NewDependency()
Please note that if you update a dependency, then it will be updated in all the places where it is used.
