propertywrapper.swift

@propertyWrapper
struct Injected<Service> {

    typealias DelayedInjection = () -> Service

    var service: Service?
    var delayed: DelayedInjection?

    init() {
        delayed = { Dependencies.main.resolve() } 
    }

    var wrappedValue: Service {
        mutating get {
            if let service = service {
                return service
            } else if let delayed = delayed {
                service = delayed()
                return service!
            } else {
                fatalError()
            }
        }
    }
}