swift 错误处理

// 定义错误,用来表示数组访问错误

enum ShoppingError:Error{  

    caseGoodsNotExist(String)  

    caseGoodsNotEnough(String)

    casepayNotEnough(String)

}

classShopping {  

    vargoodsList = ["可口可乐":(price:3.0,number:100),

                     "百事薯片":(price:8.0,number:200),

                     "士力架":(price:6.0,number:300),

        "阿尔卑斯":(price:3.0,number:200),

        "肉粒多":(price:28.0,number:700),

    ]

 funcbuyGoods(name:String,num:Int,pay:Double)throws->Void{

        guardletgoods =goodsList[name]else{

            throwShoppingError.GoodsNotExist("商品不存在")

        }

        guardgoods.number >= numelse{

            throwShoppingError.GoodsNotEnough("库存不足")

        }

        guardpay >= (goods.price *Double(num))  else{

            throwShoppingError.payNotEnough("金额不足")

        }

        letleftMemoey = pay - goods.price *Double(num)

        // 打印清单

        print("\(name)  \(goods.price)  \(num)  \(leftMemoey)")

    }

}

var s = Shopping()

do{

    trys.buyGoods(name:"可口可乐", num:10, pay:1)

}catchShoppingError.GoodsNotExist{

    print("商品不存在")

}catchShoppingError.GoodsNotEnough{

    print("库存不足")

}catchShoppingError.payNotEnough{

    print("金融不足")

}