if_let.swift

if let laptop = programmer.laptop {                  // set the value of laptop if `programmer.laptop` is not nil and
                                                     // enter into if-case or enter into `else` case.
    if let laptopFan = laptop.fan {                  // set the value of laptopFanName if `laptop.fan` is not nil and
                                                     // enter into if-case or enter into `else` case.
        print("\(laptop.name) contains \(laptopFan.name) fan")
    } else {
        print("\(laptop.name) contains no fan")       // Note: String interpolation "\(value)"
    }
} else {
    print("\(programmer.name) have no laptop")
}