How to implement Dependency Injection in Swift!

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[v_pradeilles]

Did you enjoy this introduction to Dependency Injection in Swift? Let me know in the comments 🚀

[ivan]

Thanks! Could be useful a new video explains how to manage dependency injections classes with a big project

[nashtravelandlifestyle]

Thoroughly explained, don't the objects in the dependency manager stay longer than needed?

[deepeshnitk]

Thanks Vincent for the video it does solve the problem of taking away the responsibility of the scene delegate to create the first ViewController. However I have a few questions with the Dependency provider structure which you have presented and would really like to get your view on my questions below.

1. Is there a better way to create Dependency provider ? .

2. Currently your DependencyProvider is a struct and it creates ViewModel and ViewController within it which I assume are a class. So in theory your struct is having class instances.

3. Is it really required for the struct to have static variables ? Can DependencyProvider just be a class with all the variables in it ?

[MarkosDarkin]

Awesome video and love your channel. Just wanted to suggest another specific approach when injecting dependencies to storyboard view controllers.
Storyboard ViewControllers with dependency injection have a problem of breaking encapsulation due to the fact you have to keep your dependencies public thus risking it being overwritten from the outside at a later time.
This approach prevents that (though I honestly just prefer to use programmatic view controller to avoid the whole thing completely):

class ViewController: UIViewController {
//Can remain private since we are using inner static init.
private var someDependency: SomeDependency!

//Static init
static func instantiate(someDependency: SomeDependency) -> Self {
let vc = UIStoryboard(name: "Main", bundle: nil)
"Identifier") as! Self
vc.someDependency = someDependency
return vc
}

override func viewDidLoad() {
super.viewDidLoad()
//Use dependency here
}
}

[HumbleHustle]

Hi, nice video. I often get asked the interview question. "Imagine if you have really large array what will be most appropriate way to handle it will you use value type or reference type?" I will really appreciate if you make a video addressing this. Merci bonne journée

[byaruhaf]

Thanks, Vincent for this introduction, just wondering shouldn't the class TesService conform to the protocol Servicing and not inherit from class Service

[imatricepte]

Hey, thanks for this video !
I wonder what's the implem when it comes to having a lot of VCs ? do you create multiples DependencyProvider ? what about navigation ?

[smilebot]

actually, I don't think this does test the actual method which could still be being called twice. i doubt we would want to call the method `getData(_:)` directly in a unit test anyway assuming it's concurrent and hits an external dependency.

[nomadromrom]

XCTestExpectation seems more appropriate to use for checking that the viewModel calls the service only once

class MockedService: Servicing {

let expectation = "callCount")

func getData(_ completion: @escaping (Int) -> Void) {
expectation.fulfill()
}

}

class ViewModelTests: XCTestCase {

func testViewModelCallsService() {
let service = MockedService()
let vm = ViewModel(service: service)
vm.fetchData()
wait(for: [service.expectation], timeout: 1)
}

}

[priyacooking]

How can this be done in SwiftUI ? or is dependency injection not needed in SwiftUI ?

[Nairda]

Why is the DependencyProvider a struct and not a class?