How to create dependency injection in swift?

In software engineering, dependency injection is a technique whereby one object supplies the dependencies of another object. A “dependency” is an object that can be used, for example as a service. Instead of a client specifying which service it will use, something tells the client what service to use. According to Wikipedia: https://en.wikipedia.org/wiki/Dependency_injection

Dependency injection is nothing but it is style of writing code and way of constructing object where we can say yes my code is totally de-coupled and When we are testing our objects, we can easily set up unit tests and replace our dependency for another property of its type. Three-way to create it.

There is three-way to write code as dependency injection.

1. Property injection — In this way we inject property from outside.

class CameraViewModel {
     var camera = Camera?
}
let cameraViewModel = CameraViewModel()
let customCamera = Camera() // Individual creation
cameraViewModel.camera = customCamera // here customCamera is injecting to viewModel via property.

2. Constructor/Initializer : Inject object at the time of creation

class CameraViewModel {
    var camera: Camera
    init(customCamera: Camera) {
        self.camera = customCamera
       }
}
// Calling time
let customCamera = Camera() // Individual creation
let cameraViewModel = CameraViewModel(customeCamera) //injected by constructor

3. Via Protocol/interface Method : Inject it when call method

class Film {
}
protocol CameraManager {
func showInPortrate(in customCamera: Camera)
}
extension Film : CameraManager {
      func showInPortrate(in customCamera: Camera) {
           print(customCamera)
          }
}

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