struct.swift

struct Tomato {
    var name: String
    var state: Bool // true=active, false=pause
    var start_time: Date
    var finish_time: Date
    var elapsed_time: TimeInterval
    
    mutating func toggle() {
        state = !state
    }
    
    mutating func finish() {
        finish_time = Date()
        state = false
        elapsed_time = start_time.distance(to: finish_time)
    }
}

var tomato: Tomato = Tomato(name: "Composing Fundamental Swift Articles", state: true, start_time: Date(), finish_time: Date(), elapsed_time: 0)

print(tomato)
tomato.toggle()
print(tomato.state)
tomato.finish()
print(tomato.elapsed_time)