Injectable

injectable.swift

struct Injector {
    func inject() -> String {
        "testing 123" // simplified inject function
    }
}

protocol Injectable {
    static func inject(_ injector: Injector) -> Self
}

struct MyStruct: Injectable {
    let value: String

    static func inject(_ injector: Injector) -> Self {
        Self(value: injector.inject())
    }
}

let injector = Injector()

func get<T>() -> T? {
    let type = T.self
    if type is Injectable.Type {
        return (type as! Injectable.Type).inject(injector) as? T
    }
    // Would normally throw instead of returning nil
    return nil
}

let myStruct: MyStruct? = get()
let myInt: Int? = get()

print("my struct: \(myStruct?.value ?? "")")
print("int: \(myInt ?? 0)")