检查对象是否包含在数组

Question

我有这个问题，而且我对Swift更新。我试过在互联网上四处寻找并找到看起来正确的东西，但出于某种原因我无法使用它。这是我正在使用的片段：

    /** This struct is meant to hold all of the information taken from the firebase database */
    struct Service {
    var name: String
    var description: String
    var hours: String
    var type: String
    var estimated_payment: String
    var ge_min_payment: String
    var hourly_rate: String
    var income_category: String
    var part_cost: String
    var part_markup: String
    var standard_price: String
    var task_number: String
    var ttsp_price: String
    var ttsp_savings: String
    var agreement_discount: String
    var annual_part_increase: String
}

  // ...

  /** cartArray contains all the objects currently in the cart for checkout */
  var cartArray: [Service] = []

  // ....  

  /**
    * isInCart
    *
    * a boolean function which checks to see if a specific service object is in the array
    */
    func isInCart(service: Service) -> Bool {
        var contained = self.cartArray.contains(service)
        return contained ? true : false;
    }

当我尝试编译这个项目时，这是我收到的错误：

我对这有什么问题感到有些困惑。有人可以帮忙吗？