0001-single-source-of-truth-011.swift

// We create a protocol for formatting a name
protocol NameFormatterType {
    func format(name: String) -> String
}

// A concrete implementation adds a prefix "Sir" to the given name.
struct SirFormatter: NameFormatterType {
    func format(name: String) -> String {
        "Sir \(name)"
    }
}

// We will register that implementation
Dependencies.Container.default.register(SirFormatter())

// Apart from that, we have a Person struct.
struct Person {
    // We INJECT the NameFormatterType dependency using our handy annotation.
    @Dependencies.Inject() private var formatter: NameFormatterType
    
    let name: String
    
    // And in any part of the struct code we can use the injected dependency
    func present() {
        print("Hi, I am \(formatter.format(name: name))")
    }
}

let fernando = Person(name: "Fernando")
fernando.present() // Will print: "Hi, I am Sir Fernando"