Open Radar

 
Summary:
To be able to initialize a view controller with a view defined in a storyboard from code you have to use:
- UIStoryboard.instantiateViewController(withIdentifier:) or
- UIStoryboard.instantiateInitialViewController()

Those methods in turn call init(coder:) on the view controller. This doesn't play well with Swift's optionality. If the view controller requires some data to be set on it to work it has to use properties that are either optional or have an implicitly unwrapped optional attribute:
- var dependency: SomeType? or
- var dependency: SomeType!

So, the fact that some dependency wasn't set can be found only at runtime. If UIStoryboard had a method like `decoder(forViewControllerIdentifier identifier: String) -> NSCoder` it would be possible to define an initializer on a view controller that takes both that NSCoder instance and all other objects that it requires to work, e.g.:

class DetailsViewController: UIViewController {

    let dependency: SomeType

    init?(coder aDecoder: NSCoder, dependency: SomeType) {
        self.dependency = dependency
        super.init(coder: aDecoder)
    }
}

We could then initialize it by calling that init directly:
let detailsViewController = DetailsViewController(coder: decoder, dependency: dependency)

This would solve a common issue of not being able to use dependency injection via initializer. At least when we don't use segues.


Expected Results:
We should be able to use dependency injection via initalizer when using storyboards (which provide really nice features!).


Actual Results:
We aren't able to use dependency injection via initializer with storyboards.


Notes:
Based on a blog post: http://holko.pl/2016/12/14/storyboards-dependency-injection/